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Volume 12
Issue 6
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Metals, Volume 12, Issue 6 (June 2022) – 167 articles

Cover Story (view full-size image): The archaeological iron from the “Nanhai I” was a typical hypereutectic white cast iron with eutectic ledeburite and primary cementite. The cementite was formed into a net structure. In the marine, the ferrite surrounded by cementite corroded preferentially, and corrosion products in different structures underwent phase transformation continually. The volume of corrosion products expanded, accumulating large internal stresses locally. Because the plasticity of the cementite was almost zero, it was torn apart under stress, forming many microcracks and fissures up to several microns. Eventually, a complete iron artifact will become brittle and even pulverized at a macroscopic point of view. View this paper
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13 pages, 4603 KiB  
Article
Influence of Basicity and Calcium-Containing Substances on the Consolidation Mechanism of Fluxed Iron Ore Pellets
by Kuo Liu, Feng Chen, Yufeng Guo, Yajing Liu, Shuai Wang and Lingzhi Yang
Metals 2022, 12(6), 1057; https://doi.org/10.3390/met12061057 - 20 Jun 2022
Cited by 7 | Viewed by 2243
Abstract
The application of fluxed pellets in iron making industry has attracted considerable attention because of the better metallurgical properties than acid pellets and environmental friendliness compared to sinters. However, fluxed pellets with different binary basicity (CaO/SiO2) exhibited significant differences in phase [...] Read more.
The application of fluxed pellets in iron making industry has attracted considerable attention because of the better metallurgical properties than acid pellets and environmental friendliness compared to sinters. However, fluxed pellets with different binary basicity (CaO/SiO2) exhibited significant differences in phase composition, microstructure and consolidation mechanism. These differences mainly stemmed from the influence of calcium-containing substances in fluxed pellets. Herein, the theoretical investigation discovered the calcium-containing substances from fluxed pellets, including calcium iron silicate, calcium silicate and complex calcium ferrite (SFCA), which determined the properties of fluxed pellets. Microstructure analysis revealed that the calcium-containing substances filled between hematite particles were used as a binding phase to assist in pellets’ consolidation. Furthermore, the calcium-containing binding phase formed in the low-basicity (0.4–1.0) pellets was mainly composed of the calcium iron silicate glassy phase, while the binding phase of the high-basicity (1.0–1.2) pellets was dominated by SFCA belonging to SiO2-Fe2O3-CaO-Al2O3 multivariate system. In comparison, SFCA exhibited better crystallinity and reducibility than calcium iron silicate. Within the roasting temperature range of 1200–1250 °C, the increase of basicity contributed to the fluxed pellets obtaining better strength. To sum up, fluxed pellets with SFCA as the main calcium-containing binding phase can be obtained by increasing the basicity above 1.0–1.2, which was imperative for further improving the physical and metallurgical properties of fluxed pellets. Full article
(This article belongs to the Topic Advances in Sintering and Pellet Technology)
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15 pages, 3210 KiB  
Article
Solvent Extraction for Separation of 99.9% Pure Cobalt and Recovery of Li, Ni, Fe, Cu, Al from Spent LIBs
by Pratima Meshram, Sami Virolainen, Abhilash and Tuomo Sainio
Metals 2022, 12(6), 1056; https://doi.org/10.3390/met12061056 - 20 Jun 2022
Cited by 16 | Viewed by 6791
Abstract
In this work, hydrometallurgical recycling of metals from high-cobalt-content spent lithium-ion batteries (LIBs) from laptops was studied using precipitation and solvent extraction as alternative purification processes. Large amounts of cobalt (58% by weight), along with nickel (6.2%), manganese (3.06%) and lithium (6.09%) are [...] Read more.
In this work, hydrometallurgical recycling of metals from high-cobalt-content spent lithium-ion batteries (LIBs) from laptops was studied using precipitation and solvent extraction as alternative purification processes. Large amounts of cobalt (58% by weight), along with nickel (6.2%), manganese (3.06%) and lithium (6.09%) are present in LiCoO2 and Li2CoMn3O8 as prominent Co-rich phases of the electrode material. The pregnant leach solution (PLS) that was generated by leaching in the presence of 10% H2O2 using 50 g/L pulp density at 80 °C for 4 h contained 27.4 g/L Co, 3.21 g/L Ni, 1.59 g/L Mn and 3.60 g/L Li. The PLS was subjected to precipitation at various pH using 2 M NaOH but the purification performance was poor. To improve the separation of Mn and other impurities and in order to avoid the loss of cobalt and nickel, separation studies were carried out using a solvent extraction technique using di-(2-ethylhexyl) phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272). Overall, this study examines the fundamentals of separating and synthesizing 99.9% pure Co sulfate from leach liquor of spent laptop LIBs with remarkably high cobalt content. Full article
(This article belongs to the Special Issue Extractive Metallurgy for the Sustainable Supply of Metals in Lithium-Ion Batteries)
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14 pages, 32909 KiB  
Article
Magneto-Optical Imaging of Arbitrarily Distributed Defects in Welds under Combined Magnetic Field
by Nvjie Ma, Xiangdong Gao, Meng Tian, Congyi Wang, Yanxi Zhang and Perry P. Gao
Metals 2022, 12(6), 1055; https://doi.org/10.3390/met12061055 - 20 Jun 2022
Cited by 9 | Viewed by 1857
Abstract
Using the traditional magneto-optical detection methods, micro-weld defects parallel with the magnetic field direction may be overlooked. In order to overcome this, a non-destructive testing method based on magneto-optical imaging under a vertical combined magnetic field (VCMF) is proposed. To demonstrate this, the [...] Read more.
Using the traditional magneto-optical detection methods, micro-weld defects parallel with the magnetic field direction may be overlooked. In order to overcome this, a non-destructive testing method based on magneto-optical imaging under a vertical combined magnetic field (VCMF) is proposed. To demonstrate this, the experimental results of the magneto-optical imaging of weld defects excited by a vertical combined magnetic field (VCMF) or parallel combined magnetic field (PCMF) are compared with those of traditional magnetic fields (constant magnetic field (CMF), alternating magnetic field (AMF), and rotating magnetic field (RMF)). It is found that the magneto-optical imaging under a VCMF can accurately detect weld defects of any shape and distribution. In addition, the center difference method is used to eliminate the influence of noise on the defect contour extraction of magneto-optical images, and the active contour of weld defects in the magneto-optical images is extracted. The results show that many noises can be identifiedby the robustness of the level set method, operating in low-pass filtering, so that much information that is usually lost can be retained. Full article
(This article belongs to the Section Welding and Joining)
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16 pages, 10408 KiB  
Article
Effect of Grain Size on the Properties of Aluminum Matrix Composites with Graphene
by Irina Brodova, Liudmila Yolshina, Sergey Razorenov, Dmitriy Rasposienko, Anastasia Petrova, Irina Shirinkina, Evgeny Shorokhov, Roman Muradymov, Gennady Garkushin and Andrey Savinykh
Metals 2022, 12(6), 1054; https://doi.org/10.3390/met12061054 - 20 Jun 2022
Cited by 12 | Viewed by 2993
Abstract
The structure and mechanical properties of composites consisting of a metal matrix based on aluminum and its alloys of different compositions (AA-3003 and AA-5154) and graphene synthes sized in situ under a layer of molten salts were investigated depending on the chemical composition [...] Read more.
The structure and mechanical properties of composites consisting of a metal matrix based on aluminum and its alloys of different compositions (AA-3003 and AA-5154) and graphene synthes sized in situ under a layer of molten salts were investigated depending on the chemical composition and grain size of the matrix. Aluminum matrix composites of three compositions were studied in as-cast coarse-grained, deformed fine-grained (grain size < 1 mm), and deformed sub microcrystalline (grain size < 1 μm) states in order to compare the structural characteristics of composites with different grain sizes. The composites were subjected to deformation with a split Hopkinson (Kolsky) bar and to dynamic-channel angular pressing. The hardness and dynamic mechanical properties of the composites were measured at strain rates ε˙ from 1.8 − 4.7 × 103 to 1.6 − 2.4 × 105 s−1. It was found that grain refinement induced a sharp increase in the hardness of composites with various compositions (by a factor of 1.6–2.6). A correlation of the elastic-plastic properties of the aluminum matrix composites with the grain sizes and chemical compositions of the matrices was established. A transition from coarse-grained to sub microcrystalline structure was shown to improve the elastic-plastic properties on average by a factor of 1.5. It was proved that the reinforcing effect of graphene increased with the decreasing grain size of the matrix. Mechanisms of reinforcement of the aluminum matrix composites using graphene were proposed. Full article
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10 pages, 1099 KiB  
Article
Solvent Extraction of Metal Ions from Synthetic Copper Leaching Solution Using R4NCy
by Rossana Sepúlveda, Norman Toro, Pía Hernández, Patricio Navarro, Cristian Vargas, Edelmira Gálvez and Jonathan Castillo
Metals 2022, 12(6), 1053; https://doi.org/10.3390/met12061053 - 20 Jun 2022
Cited by 6 | Viewed by 2496
Abstract
Recent works suggest that the use of ionic liquids in the copper solvent extraction industry is feasible. However, the reports did not use real solutions (or synthetic solutions with various elements). This fact remains poorly established, and the interaction efficiencies are still under [...] Read more.
Recent works suggest that the use of ionic liquids in the copper solvent extraction industry is feasible. However, the reports did not use real solutions (or synthetic solutions with various elements). This fact remains poorly established, and the interaction efficiencies are still under study. The objective of this research is to explore the extraction and stripping of the four major elements present in a copper industrial pregnant leach solution (Cu(II), Fe(III), Mn(II), and Zn(II)) using the methyltrioctyl/decylammonium bis(2,4,4-trimethylpentyl)phosphinate (R4NCy) ionic liquid as an extractant. The work conditions studied in extraction were ionic liquid concentration, initial pH, and O/A ratio, and in stripping were H2SO4 concentration and O/A ratio. The test was carried out at room temperature and ambient pressure. High efficiency and selectivity (99.82% and 113,755 over Cu(II), respectively) were observed for Fe(III) extraction over the other elements. Moreover, after the extraction test, significant difficulty in stripping Fe(III) loaded in the ionic liquid was observed (28.7% at 0.5 M of H2SO4). Finally, the present study demonstrates that the R4NCy ionic liquid is not suitable for copper extraction because it has a higher selectivity for Fe(III) and Zn(II). Full article
(This article belongs to the Special Issue Advances in Metal Extraction and Recycling)
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13 pages, 5065 KiB  
Article
Doped Potassium Jarosite: Synthesis, Characterization and Evaluation as Biomaterial for Its Application in Bone Tissue Engineering
by Juan R. Serralde-Lealba, Eduardo Cerecedo-Sáenz, Juan Hernández-Ávila, Alberto Arenas-Flores, María A. Veloz-Rodríguez, María del P. Gutiérrez-Amador, Arely M. González-González, Raúl Rosales-Ibáñez and Eleazar Salinas-Rodríguez
Metals 2022, 12(6), 1052; https://doi.org/10.3390/met12061052 - 20 Jun 2022
Cited by 3 | Viewed by 2250
Abstract
For decades, jarosites have been precipitated by controlling Fe in hydrometallurgical circuits. In addition, their synthesis, characterization, precious metals incorporation, decomposition and leaching have led to important results in this field. Nowadays, new topics related to the synthesis of these compounds have directed [...] Read more.
For decades, jarosites have been precipitated by controlling Fe in hydrometallurgical circuits. In addition, their synthesis, characterization, precious metals incorporation, decomposition and leaching have led to important results in this field. Nowadays, new topics related to the synthesis of these compounds have directed studies for applications such as lithium-ion batteries (as cathodes or/and anodes). Additionally, in this work, the evaluation of these kinds of compounds as biomaterials to be used in bone tissue engineering is shown, which is a novel application of these jarosite type-compounds. The method used for the synthesis of these compounds has been improved, decreasing the temperature (from 95 to 70 °C) and synthesis time (from 24 to only 3 h), which allows the doping of the potassium jarosite with calcium, strontium and magnesium (JKCa, JKCa2 and JKAll). The powders obtained this way were characterized confirming the incorporation of these elements into the structure, and the biological assays allowing the cell proliferation at 10 days conclude that these compounds are viable as a biomaterial, due to their non-toxic property. On the other hand, these jarosites show osteoinduction when added to the swine dental pulp stem cells and can be used for orthodontic purpouses. Full article
(This article belongs to the Special Issue Jarosites: Structure, Formation, Leaching, Environmental, Applications)
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32 pages, 6047 KiB  
Review
Advanced High-Strength Steels for Automotive Applications: Arc and Laser Welding Process, Properties, and Challenges
by Ashok Kumar Perka, Merbin John, Udaya Bhat Kuruveri and Pradeep L. Menezes
Metals 2022, 12(6), 1051; https://doi.org/10.3390/met12061051 - 20 Jun 2022
Cited by 36 | Viewed by 8636
Abstract
In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by [...] Read more.
In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by following fusion welding techniques, such as gas metal arc welding, tungsten inert gas welding, and laser welding. These fusion welding techniques often lead to a loss of mechanical properties due to the weld thermal cycles in the heat-affected zone (HAZ) and the deposited filler wire chemistry. This review paper elucidates the current studies on the state-of-the-art of weldability on AHSS, with ultimate strength levels above 800 MPa. The effects of alloy designs on the HAZ softening, microstructure evolution, and the mechanical properties of the weld joints corresponding to different welding techniques and filler wire chemistry are discussed. More specifically, the fusion welding techniques used for the welding of AHSS were summarized. This review article gives an insight into the issues while selecting a particular fusion welding technique for the welding of AHSS. Full article
(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)
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20 pages, 16707 KiB  
Article
Numerical Simulation of Flow Field, Bubble Distribution and Solidified Shell in Slab Mold under Different EMBr Conditions Assisted with High-Temperature Quantitative Velocity Measurement
by Yi Guo, Jian Yang, Yibo Liu, Wenyuan He, Changliang Zhao and Yanqiang Liu
Metals 2022, 12(6), 1050; https://doi.org/10.3390/met12061050 - 19 Jun 2022
Cited by 5 | Viewed by 1850
Abstract
The flow field, bubble distribution and solidified shell in slab mold are numerically simulated with large eddy simulation (LES) under different electromagnetic braking (EMBr) conditions, assisted with high-temperature quantitative velocity measurement. The calculated velocities on the mold surface are in good agreement with [...] Read more.
The flow field, bubble distribution and solidified shell in slab mold are numerically simulated with large eddy simulation (LES) under different electromagnetic braking (EMBr) conditions, assisted with high-temperature quantitative velocity measurement. The calculated velocities on the mold surface are in good agreement with the measured values of the industrial experiment at high temperature with the rod deflection method under different EMBr conditions and different argon flow rates, which verifies the correctness of the model. After EMBr is applied, the flow velocity on the surface of the mold decreases. With EMBr, the velocity on the mold surface first increases and then decreases with the increase in argon flow rate. When the argon flow rate is 10 L·min−1, the jets at the side ports of the submerged entry nozzle (SEN) become disordered, and the liquid level fluctuation near the SEN wall intensifies, which increases the risk of slag entrainment and slag layer breaking and the risk of argon bubbles being captured. When the argon flow rate is 6 L·min−1, the velocity and fluctuation on the mold surface can be significantly reduced by use of double-ruler EMBr; the impact of the jet on the narrow face of the mold is obviously restrained; and the solidified shell thickness increases. Full article
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8 pages, 3717 KiB  
Article
The Mechanism of Oxide Growth on Pure Aluminum in Ultra-High-Temperature Steam
by Lin Huang, Ke Xiong, Xiaofeng Wang, Xi He, Lin Yu, Chaokun Fu, Xiaodong Zhu and Wei Feng
Metals 2022, 12(6), 1049; https://doi.org/10.3390/met12061049 - 19 Jun 2022
Cited by 1 | Viewed by 3401
Abstract
A high-temperature water steam (H2O(g)) between 300 °C and 1000 °C reacted with the Al surface in this study. The Al surface states were characterized and analyzed using XRD °C, XPS, and SEM after and before the reaction, and the effects [...] Read more.
A high-temperature water steam (H2O(g)) between 300 °C and 1000 °C reacted with the Al surface in this study. The Al surface states were characterized and analyzed using XRD °C, XPS, and SEM after and before the reaction, and the effects and mechanism of H2O(g) on the Al surface morphology and chemical composition were studied. The experiment showed that for an Al sheet reacting with H2O(g), its oxide layer morphology changed from nano-needle to flaky and granular oxides gradually with the rise of temperature, and finally the Al surface became porous as a whole. Its oxide crystals were amorphous and were determined to be aluminum oxide (Al2O3) using XPS. The needle-like oxide in the Al sheet surface tended to grow toward the surface, and no obviously inward oxidizing corrosion layer occurred in the aluminum substrate; the oxide layer between the oxide and Al sheet substrate was compact, and could effectively prevent the infiltration and corrosion of water molecules. Full article
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16 pages, 4804 KiB  
Article
The Effect of the Shot Blasting Process on the Dynamic Response of Steel Reinforcement
by Maria Basdeki and Charis Apostolopoulos
Metals 2022, 12(6), 1048; https://doi.org/10.3390/met12061048 - 19 Jun 2022
Cited by 1 | Viewed by 1960
Abstract
As it is widely known, corrosion poses a real threat for reinforced concrete structures, especially when they are located in coastal areas. This phenomenon, in conjunction with repeated loads, such as intense seismic events, adversely affect their useful service life. Several experimental studies [...] Read more.
As it is widely known, corrosion poses a real threat for reinforced concrete structures, especially when they are located in coastal areas. This phenomenon, in conjunction with repeated loads, such as intense seismic events, adversely affect their useful service life. Several experimental studies have presented the magnitude of degradation of steel reinforcement due to corrosion in the presence of fatigue, which affects either the serviceability or durability of steel reinforcement. As a result, the current experimental study presents the results of the shot blasting process of steel reinforcement at various times of exposure to a corrosive environment and the influence on their dynamic response after the execution of low cycle fatigue tests at different constant strain amplitudes. The findings show the beneficial effect of the shot blasting process in terms of percentage mass loss and the improvement of mechanical performance of steel bars in terms of service life and energy dissipation capacity. Moreover, the assessment performed with a quality material index demonstrates the improved mechanical performance of shot blasted specimens vs. bare specimens, in the long term for medium range-imposed deformation. Full article
(This article belongs to the Special Issue Assessment of Corrosion Resistance and Mechanical Properties of Reinforced Concrete)
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8 pages, 3446 KiB  
Article
Influence of the Laser Deposited 316L Single Layers on Corrosion in Physiological Media
by Unai Garate, Enara Mardaras, Rodolfo González, Jon Iñaki Arrizubieta, Garikoitz Artola and Javier Aldazabal
Metals 2022, 12(6), 1047; https://doi.org/10.3390/met12061047 - 19 Jun 2022
Viewed by 1856
Abstract
A multilayer laser-deposited lining of AISI 316L stainless steel makes a regular structural steel surface corrosion resistant in physiological media. Despite the application of single-layer stainless-steel linings being economically beneficial and allowing thinner surface modifications, dilution effects that modify the pitting resistance of [...] Read more.
A multilayer laser-deposited lining of AISI 316L stainless steel makes a regular structural steel surface corrosion resistant in physiological media. Despite the application of single-layer stainless-steel linings being economically beneficial and allowing thinner surface modifications, dilution effects that modify the pitting resistance of the coating must be accounted for. In order to study the feasibility of employing single-layer coatings instead of multilayer coatings for corrosion protection in physiological media, a polarization testing back-to-back comparison was performed between laser-deposited AISI 316L monolayers on 42CrMo4 quenched and tempered steel and cold-rolled AISI 316L sheet in Dulbecco’s Phosphate Buffer Solution at 36 °C. A higher dispersion in pitting resistance, ranging from 800 mV to 1200 mV, was found on the coated samples, whereas the cold-rolled material was more stable in the 1200 mV range. The resulting differences in corrosion rates and pitting potentials open the discussion on whether the chemical composition deviations on AISI 316L dilution layers are acceptable in terms of surface functionality in medical devices. Full article
(This article belongs to the Special Issue Metals for Biomedical Applications: From Experiments to Computer Models)
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15 pages, 6837 KiB  
Article
Effect of Heat Treatment Prior to Direct Hot-Extrusion Processing of Al–Cu–Li Alloy
by Paula Rodríguez-González, Elisa María Ruiz-Navas and Elena Gordo
Metals 2022, 12(6), 1046; https://doi.org/10.3390/met12061046 - 19 Jun 2022
Cited by 7 | Viewed by 2683
Abstract
This study presents and explains the results of the first steps in developing high strength aluminium alloy (Al–Cu–Li) wires for the ultimate purpose of using them as feedstock for DED (directed energy deposition) techniques, such as wire arc additive manufacturing (WAAM). Powder metallurgy [...] Read more.
This study presents and explains the results of the first steps in developing high strength aluminium alloy (Al–Cu–Li) wires for the ultimate purpose of using them as feedstock for DED (directed energy deposition) techniques, such as wire arc additive manufacturing (WAAM). Powder metallurgy (PM) is proposed as the method to produce the wires due to the high flexibility to adapt the composition and the lower temperatures used with respect to casting. Two PM routes are proposed. The first route comprises blending of the powders, uniaxial pressing, and hot extrusion of the green compact to obtain a bar; the second route includes a heat treatment of the green compact, to promote the diffusion of the alloying elements before hot extrusion. Further steps, such as rolling or drawing, are necessary to obtain the wire from the bar. This work studies the effects of the processing parameters on the properties of extruded bars and compares the results of the two routes employed, with special attention paid to the effects of heat treatment. The study confirms that heat treatment homogenises the microstructure and requires higher applied extrusion force and time. The results from characterisation show the presence of Al–Cu and Al–Cu–Li phases in the microstructure. Full article
(This article belongs to the Special Issue Advances in Powder Metallurgy II)
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17 pages, 5098 KiB  
Article
Probabilistic Seismic Assessment of CoSPSW Structures Using Fragility Functions
by Zhilun Tan, Qiuhong Zhao, Yu Zhao and Cheng Yu
Metals 2022, 12(6), 1045; https://doi.org/10.3390/met12061045 - 18 Jun 2022
Cited by 4 | Viewed by 1697
Abstract
The corrugated steel plate shear wall (CoSPSW) is a new type of steel plate shear wall, in which corrugated wall plates instead of flat wall plates are adopted. The lateral stiffness and shear buckling capacity of the shear wall system could be significantly [...] Read more.
The corrugated steel plate shear wall (CoSPSW) is a new type of steel plate shear wall, in which corrugated wall plates instead of flat wall plates are adopted. The lateral stiffness and shear buckling capacity of the shear wall system could be significantly enhanced, and then, wall plate buckling under gravity loads would be mitigated. This paper presents a study on the probabilistic assessment of the seismic performance and vulnerability of CoSPSWs using fragility functions. The damage states and corresponding repair states of CoSPSWs were first established from experimental data. Then, incremental dynamic analyses were conducted on the CoSPSW structures. The structural and nonstructural fragility functions were developed, based on which the seismic performance and vulnerability of the CoSPSWs were obtained and compared with the conventional steel plate shear walls (SPSWs). It was shown that for various repair states, the 25th percentile PGA of the CoSPSW was always higher than the SPSWs with the same wall thickness and boundary frame, which indicated that the CoSPSW has a lower damage potential and better seismic performance than the SPSW. Full article
(This article belongs to the Special Issue Modelling, Test and Practice of Steel Structures)
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15 pages, 5952 KiB  
Article
Functional and Mechanical Properties of As-Deposited and Heat Treated WAAM-Built NiTi Shape-Memory Alloy
by Arthur Khismatullin, Oleg Panchenko, Dmitry Kurushkin, Ivan Kladov and Anatoly Popovich
Metals 2022, 12(6), 1044; https://doi.org/10.3390/met12061044 - 18 Jun 2022
Cited by 3 | Viewed by 2127
Abstract
In this work, MIG process was utilized for the wire arc additive manufacturing of the wall-shaped parts, using NiTi shape-memory alloy. High-scale specimens consisting of 20 layers were deposited by using Ni-rich (Ni55.56Ti wt.%) wire as a feedstock on the NiTi substrate with [...] Read more.
In this work, MIG process was utilized for the wire arc additive manufacturing of the wall-shaped parts, using NiTi shape-memory alloy. High-scale specimens consisting of 20 layers were deposited by using Ni-rich (Ni55.56Ti wt.%) wire as a feedstock on the NiTi substrate with the identical chemical composition. One of two specimens was heat-treated at a temperature of 430 °C for 1 h. The influence of such a heat treatment on the microstructure, phase transformation temperatures, chemical and phase compositions, microhardness, and tensile and bending tests’ results is discussed. As-deposited metal successfully demonstrates superelastic behavior, except in the lower zone. In regard to the shape-memory effect, it was concluded that both the as-deposited and the heat-treated samples deformed in liquid nitrogen completely restored (100%) their shapes at an initial strain of 4–5%. An occurrence of the R-phase was found in both the as-deposited and the heat-treated specimens. The phase transformation temperatures, microstructure, and tensile and bending tests results were found to be anisotropic along the height of the specimens. The presented heat treatment led to changes in the functional and mechanical properties of the specimen, provided with the formation of finely dispersed Ni4Ti3, NiTi2, and Ni3Ti phases. Full article
(This article belongs to the Special Issue Advanced Manufacturing of Novel Metallic Related Materials)
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11 pages, 4514 KiB  
Article
Mechanical Properties of the Ti49.8Ni50.2 Alloy after Multi-Axial Forging at 573 K
by Aleksandr Lotkov, Oleg Kashin, Victor Grishkov, Dorzhima Zhapova, Konstantin Krukovskii, Angelina Gusarenko, Natalia Girsova, Dmitrii Bobrov and Olga Kashina
Metals 2022, 12(6), 1043; https://doi.org/10.3390/met12061043 - 18 Jun 2022
Viewed by 1619
Abstract
The mechanical properties of Ti49.8Ni50.2 (at %) alloy under tension at room temperature are studied in dependence on the true strain (e = 1.84–9.55) specified during isothermal multi-axial forging (abc-pressing). It was found that the stress at the beginning [...] Read more.
The mechanical properties of Ti49.8Ni50.2 (at %) alloy under tension at room temperature are studied in dependence on the true strain (e = 1.84–9.55) specified during isothermal multi-axial forging (abc-pressing). It was found that the stress at the beginning of the pseudoyield plateau does not depend on the value of the true abc-strain. It was found that after abs-pressing, already at a true strain e = 1.84, the yield stress σy was 900 ± 25 MPa, which is more than twice as high as compared to σy in the initial state of the specimens. With a further increase in the abc-strain, the yield stress continues to increase slightly and reaches 1000 ± 25 MPa at e = 9.55. In this case, the ultimate tensile strength of the samples increases by about 15%. The strain-hardening coefficient ϴ = dσ/dε at the III (linear) stage of the σ(ε) curve has a similar dependence on e. It is shown that after abc-pressing with e from 1.84 to 9.55, the yield stress and ultimate tensile increase linearly with increasing d−1/2 in accordance with the Hall–Petch relation, where d is the average grain–subgrain size. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Shape Memory Alloys)
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11 pages, 4303 KiB  
Article
Vacuum Brazing of Dissimilar Al 7075 and Al–25 Si Alloy
by Dashuang Liu, Ping Wei, Weimin Long and Wei Zhou
Metals 2022, 12(6), 1042; https://doi.org/10.3390/met12061042 - 18 Jun 2022
Cited by 1 | Viewed by 1991
Abstract
The vacuum brazing of dissimilar Al 7075 and Al–25 Si alloy was investigated. The brazing filler was copper foil with a thickness of 20 μm, and the brazing temperature was 560 °C held for 10 min. The average shear strength of the brazed [...] Read more.
The vacuum brazing of dissimilar Al 7075 and Al–25 Si alloy was investigated. The brazing filler was copper foil with a thickness of 20 μm, and the brazing temperature was 560 °C held for 10 min. The average shear strength of the brazed joint of dissimilar Al 7075 and Al–25 Si alloy was 26.4 MPa. The copper layer was found to be dissolved completely, and the interface of the joint had an irregular shape with a serrated border, indicating a good metallurgical bonding between the two dissimilar alloys. However, factors which might cause deterioration of the shear strength were also observed, including the formation of the intermetallic compounds such as MgZn2, Cu2Al and Mg2Si, the existence of voids and microcracks, the coarsening of grains in Al 7075, and the coarsening of primary Si in Al–25 Si alloy. Full article
(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)
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13 pages, 29906 KiB  
Article
Improvements in the Microstructure and Mechanical Properties of Aluminium Alloys Using Ultrasonic-Assisted Laser Welding
by Ahmed Teyeb, João Silva, Jamil Kanfoud, Phil Carr, Tat-Hean Gan and Wamadeva Balachandran
Metals 2022, 12(6), 1041; https://doi.org/10.3390/met12061041 - 17 Jun 2022
Cited by 10 | Viewed by 2790
Abstract
Welding high-strength aluminium alloys is generally a delicate operation due to the degradation of mechanical properties in the thermally affected zone (TAZ) and the presence of porosities in the molten metal. Furthermore, aluminium alloys contain compounds that solidify before the rest of the [...] Read more.
Welding high-strength aluminium alloys is generally a delicate operation due to the degradation of mechanical properties in the thermally affected zone (TAZ) and the presence of porosities in the molten metal. Furthermore, aluminium alloys contain compounds that solidify before the rest of the base alloy, therefore acting as stress concentration points that lead to the phenomenon of hot cracking. This paper investigates the process of applying ultrasonic vibrations to the molten pool aluminium alloy AA6082 to improve both its microstructure and mechanical properties. We analysed conventional and ultrasonic-assisted laser welding processes to assess the sonication effect in the ultrasonic band 20–40 kHz. Destructive and nondestructive tests were used to compare ultrasonically processed samples to baseline samples. We achieved a 26% increase in the tensile and weld yield strengths of laser welds in the aluminium plates via the power ultrasonic irradiation of the welds under optimum ultrasonic variable values during welding. It is estimated that the ultrasound intensity in the weld melt, using a maximum power of 160 W from a pair of 28 kHz transducers, was 35.5 W/cm2 as a spatial average and 142 W/cm2 at the antinodes. Cavitation activity was significant and sometimes a main contributor to the achieved improvements in weld quality. Full article
(This article belongs to the Special Issue Laser Welding and Welding Joint Quality Assessment - State of Art)
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20 pages, 6635 KiB  
Article
Assessing Microstructure Tensile Properties Relationships in Al-7Si-Mg Alloys via Multiple Regression
by Cássio Silva, André Barros, Talita Vida, Amauri Garcia, Noé Cheung, Danieli A. P. Reis and Crystopher Brito
Metals 2022, 12(6), 1040; https://doi.org/10.3390/met12061040 - 17 Jun 2022
Cited by 7 | Viewed by 2191
Abstract
The development of Al-based alloys presumes a detailed understanding of the microstructure evolution during solidification since the as-solidified microstructure also has effects on the subsequent thermo-mechanical processing. In the present investigation Al-7wt.%Si-xMg (x = 0.5 and 1 wt.%) alloys are subjected to transient [...] Read more.
The development of Al-based alloys presumes a detailed understanding of the microstructure evolution during solidification since the as-solidified microstructure also has effects on the subsequent thermo-mechanical processing. In the present investigation Al-7wt.%Si-xMg (x = 0.5 and 1 wt.%) alloys are subjected to transient directional solidification with a view to characterizing the microstructure evolution, with special focus on both dendritic evolution and the inherent features of the Mg2Si and π-AlSiFeMg intermetallics. Experimental power-type functions relating the primary, secondary and tertiary interdendritic spacings to the solidification cooling rate and growth rate are developed. It is observed that the Mg content added to the Al-7wt.%Si alloy and the consequent increase in the Mg2Si fraction tends to increase the values of the primary dendritic spacing. However, this same behavior is not verified for the growth evolution of dendritic side branches. A multiple linear regression (MLR) analysis is developed permitting quantitative correlations for the prediction of tensile properties and hardness from microstructural parameters to be established. The increase in the Mg alloy content from 0.5 to 1 was shown to promote an increase in both the ultimate tensile strength (σu) and elongation. Full article
(This article belongs to the Special Issue Microstructure, Mechanical Properties and Solidification Behavior of Metals and Alloys)
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10 pages, 3542 KiB  
Article
Microstructure and Corrosion Properties of Wire Arc Additively Manufactured Multi-Trace and Multilayer Stainless Steel 321
by Xiaoli Wang, Qingxian Hu, Wenkang Liu, Wei Yuan, Xinwang Shen, Fengyin Gao, Douxi Tang and Zichen Hu
Metals 2022, 12(6), 1039; https://doi.org/10.3390/met12061039 - 17 Jun 2022
Cited by 9 | Viewed by 2332
Abstract
Because low thermal conductivity and high viscosity are common characteristics of austenitic steel, it is easy to cause a large amount of heat accumulation in the chip area, resulting in tool edge collapse or wear, and the traditional preparation method is unsuitable for [...] Read more.
Because low thermal conductivity and high viscosity are common characteristics of austenitic steel, it is easy to cause a large amount of heat accumulation in the chip area, resulting in tool edge collapse or wear, and the traditional preparation method is unsuitable for preparing large and complex austenitic steel components. Wire + arc additive manufacturing (WAAM) provides a great application value for austenitic stainless steel because it can solve this problem. The cold metal transfer (CMT)-WAAM system with good control of heat input was used to fabricate the multi-trace and multilayer stainless steel 321 (SS 321) workpiece in this study. The microstructure and corrosion properties of the SS 321 workpiece were observed and compared with those of an SS 321 sheet. The results showed that the microstructure of the SS 321 workpiece from top to bottom was regularly and periodically repeated from the overlapping remelting zone, inter-layer remelting zone, and primary melting zone. There was white austenite matrix and black ferrite, and a small amount of skeleton and worm ferrite was distributed on the white austenite matrix. The average hardness value from the top to the bottom region was approximately uniform, indicating that the workpiece had good consistency. The corrosion properties in 0.5 mol/L H2SO4 solutions were compared between the SS 321 workpiece and the SS 321 sheet. The results showed that the corrosion properties of the top region of the workpiece were better than that of the middle and bottom part, and the corrosion properties of the SS 321 workpiece were better than that of the SS 321 sheet. Full article
(This article belongs to the Special Issue Prequalifying Emergency Welding (Temper Bead Welding))
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12 pages, 4915 KiB  
Article
Hg/Se/PbSO4 Recovery by Microwave-Intensified HgSe Pyrolysis from Toxic Acid Mud
by Hanlin Zeng, Peng Liu, Yan Hong, Kun Yang and Libo Zhang
Metals 2022, 12(6), 1038; https://doi.org/10.3390/met12061038 - 17 Jun 2022
Cited by 3 | Viewed by 1754
Abstract
The acid mud produced in the nonferrous smelting process is a hazardous waste, which mainly consists of elements Hg, Se, and Pb. Valuable metal (Hg/Se/Pb) can be recovered from acid mud by heat treatment. For safe disposal of the toxic acid mud, a [...] Read more.
The acid mud produced in the nonferrous smelting process is a hazardous waste, which mainly consists of elements Hg, Se, and Pb. Valuable metal (Hg/Se/Pb) can be recovered from acid mud by heat treatment. For safe disposal of the toxic acid mud, a new resource utilization technology by microwave roasting is proposed in this paper. The reaction mechanisms were revealed through thermodynamics and thermogravimetric analysis, which showed that the main reaction was the oxidative pyrolysis of HgSe in the process of roasting. Moreover, the mercury removal effects of acid mud by microwave heating and conventional heating were studied, the recovery rate of mercury by microwave heating for 30 min at 400 °C was 99.5%: far higher than that of conventional heating for 30 min at 500 °C (44.3%). This was due to the high dielectric constant of HgSe, as microwaves can preferentially heat HgSe and reduce the adsorption energy of HgSe on the surface of PbSO4 blocks, thus strengthening the pyrolysis process of HgSe and reducing energy consumption. The preferable prototyping technology for resource utilization of toxic acid mud should be microwave roasting. This study is of great significance for the realization of mercury pollution reduction and for green production of lead-zinc smelting. Full article
(This article belongs to the Special Issue Recovery and Recycling of Metals from the Wastes of New Energy Industry)
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13 pages, 5512 KiB  
Article
Effect of Zn and Cu Addition on Microstructure and Mechanical Properties of Al-10wt%Mg Alloy
by Xinbiao Wang, Shengfa Liu and Yaojun Lin
Metals 2022, 12(6), 1037; https://doi.org/10.3390/met12061037 - 17 Jun 2022
Cited by 1 | Viewed by 2500
Abstract
5xxx series aluminum alloys have been widely used in automobiles, ships, aerospace and other fields for their low density, good corrosion resistance and weldability. The present study designs a new Al-10.0Mg-1.0Zn-0.15Cu (wt%) alloy with different composition from the traditional 5xxx series and 7xxx [...] Read more.
5xxx series aluminum alloys have been widely used in automobiles, ships, aerospace and other fields for their low density, good corrosion resistance and weldability. The present study designs a new Al-10.0Mg-1.0Zn-0.15Cu (wt%) alloy with different composition from the traditional 5xxx series and 7xxx series aluminum alloys; the Zn/Mg ratio is below 1.0. Detailed characterization by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) has been carried out to reveal the microstructural evolution. The results show that the addition of Zn and Cu inhibits the precipitation of the Al3Mg2 phase in the traditional Al-Mg binary alloy during annealing and promotes the precipitation of T-Mg32(Al,Zn)49 phase, which contributes to precipitation strengthening. After 75% rolling and 150 °C annealing, the T-Mg32(Al,Zn)49 phase precipitates and the alloy obtains good strength and plasticity coordination with 0.2% offset yield strength of 519 MPa and ultimate tensile strength of 653 MPa, accompanied by uniform elongation of 8.1%. The mechanisms underlying the improved strength and plasticity in the Al-10.0Mg-1.0Zn-0.15Cu (wt%) alloy are discussed. Full article
(This article belongs to the Special Issue Advanced Rolling, Heat Treatment and Electromagnetic Processing Technology of High Performance Metals)
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24 pages, 5224 KiB  
Article
Thermodynamic and Experimental Study on Migration Characteristics of Heavy Metals during the Melting Process of Incineration Fly Ash
by Yufeng Guo, Chen Gong, Lingzhi Yang, Ming Hu and Xun Hu
Metals 2022, 12(6), 1036; https://doi.org/10.3390/met12061036 - 17 Jun 2022
Cited by 3 | Viewed by 1648
Abstract
The migration characteristics of heavy metals during the melting process were one of the key factors for safe treatment and resource utilization of incineration fly ash (IFA). In this paper, the material variation of heavy metal elements of Pb, Zn, Cu, and Fe [...] Read more.
The migration characteristics of heavy metals during the melting process were one of the key factors for safe treatment and resource utilization of incineration fly ash (IFA). In this paper, the material variation of heavy metal elements of Pb, Zn, Cu, and Fe during the IFA melting process was simulated by HSC 6.0 chemistry software. The effects of melting temperature, alkalinity, atmosphere, chlorine content of raw materials, and an iron bath added to the migration characteristics, and phase transformation of selected heavy metal elements was investigated. The simulation results were also verified by experimental results. The results showed that, with the increase in temperature, the gas phase proportion of Pb, Zn, Cu, and Fe gradually increased. The alkalinity had little effect on the proportion of elements Fe and Cu in the liquid slag (LS) phase and the element Pb in the gas phase, but the increase in alkalinity could inhibit the proportion of element Zn in the gas phase. Zn mainly existed in the gas phase, and the atmosphere had little influence on the distribution of Zn. In reducing atmosphere (RA), elements Fe and Cu, which entered the liquid metal (LM) phase, were promoted, while the volatilization of Pb was restrained, which was conducive to the recovery of heavy metals. The melting process of IFA with water-washing and dechlorination had an inhibitory effect on the volatilization of Zn and Pb, but had little effect on Fe and Cu. The proportion of element Zn in the gas phase reduced from 85.84% to 9.89%. With the iron bath added in the IFA melting process, 98.42% of Cu and 82.28% of Pb entered the LM phase as metal simple substances, and 76.3% of Zn entered the gas phase as Zn (g) and ZnCl2 (g). In the experimental verification, the distribution proportions of the four heavy metals in the gas phase, LS phase, and LM phase were consistent with the simulation results. Full article
(This article belongs to the Special Issue Clean Ironmaking and Steelmaking Processes)
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11 pages, 5095 KiB  
Article
Fatigue Analysis of Long-Span Steel Truss Arched Bridge Part II: Fatigue Life Assessment of Suspenders Subjected to Dynamic Overloaded Moving Vehicles
by Peng Liu, Hongping Lu, Yixuan Chen, Jian Zhao, Luming An, Yuanqing Wang and Jianping Liu
Metals 2022, 12(6), 1035; https://doi.org/10.3390/met12061035 - 17 Jun 2022
Cited by 6 | Viewed by 2474
Abstract
In a half-through steel arched bridge, the suspenders are the critical load transfer component that transmits the deck system and traffic load to the arch rib. These suspenders are subjected to traffic and environmental vibrations and are prone to fatigue failure, especially for [...] Read more.
In a half-through steel arched bridge, the suspenders are the critical load transfer component that transmits the deck system and traffic load to the arch rib. These suspenders are subjected to traffic and environmental vibrations and are prone to fatigue failure, especially for overloaded moving vehicles. This paper aims to study the impact of moving vehicles’ overloaded rate on the fatigue performance of suspenders in a long-span three steel truss arch bridge. Based on the Mingzhu Bay steel arch bridge, a 3D finite element bridge model was first established and seven types of moving fatigue vehicle models were considered. Then the stress amplitude and dynamic response of the suspenders on the middle steel truss arch were studied under a standard, 25%, and 50% overloaded moving vehicles load. Following that, the Miner fatigue cumulative damage theory was employed to evaluate the fatigue life of the suspenders. The results show that the short suspenders in the middle steel truss arch have the shortest fatigue life but can still meet the design requirements under the standard load. However, the fatigue life of the suspenders decreases by 20% and 30% when the overloading rate reaches 25% and 50%. The fatigue life cannot meet the design requirement when the overload rate is 50%. Full article
(This article belongs to the Special Issue Modelling, Test and Practice of Steel Structures)
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12 pages, 5258 KiB  
Article
Study of the Mechanical Properties and Microstructural Response with Laser Shock Peening on 40CrMo Steel
by Xiaoming Pan, Zhiyang Gu, Hui Qiu, Aixin Feng and Jing Li
Metals 2022, 12(6), 1034; https://doi.org/10.3390/met12061034 - 17 Jun 2022
Cited by 10 | Viewed by 2286
Abstract
In this work, the purpose of the study was to explore the influence of laser shock peening (LSP) on the mechanical behavior and microstructural response of 40CrMo steel. The residual stress at depth direction and the microstructural evolution of 40CrMo steel specimens without [...] Read more.
In this work, the purpose of the study was to explore the influence of laser shock peening (LSP) on the mechanical behavior and microstructural response of 40CrMo steel. The residual stress at depth direction and the microstructural evolution of 40CrMo steel specimens without and with LSP treatments were tested by residual stress tester and transmission electron microscopy (TEM). The microhardness at depth direction and the tensile properties at room temperature were measured. Moreover, the effects of LSP on the ability to resist wear of 40CrMo steel were analyzed, and the worn morphologies characteristics were observed by scanning electron microscope (SEM). The results demonstrated that LSP led to the surface residual stress convert from tensile stress to compressive stress, while the surface compressive residual stress tested parallel to the laser path of the specimen subjected to LSP reached −425 MPa. After the LSP process, the average surface microhardness reached 338 HV, which increased by 21.58% than that of the untreated sample. LSP could enhance the strength without losing plasticity significantly, while the average tensile strength reached 1165 MPa, and the fracture elongation reached 13.9%. After a friction and wear test, the mass loss of the sample after LSP treatment reduced by 27.5% compared to the original sample. The increase in dislocation density and the formation of deformation twins generated by LSP played a key role in enhancing the mechanical behavior of 40CrMo steel. Full article
(This article belongs to the Topic Laser Surface Modification of Cemented Carbides, Superalloys, Composites, and Alloys)
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16 pages, 6288 KiB  
Article
Corrosion Behavior of Passivated Martensitic and Semi-Austenitic Precipitation Hardening Stainless Steel
by Facundo Almeraya-Calderón, Oliver Samaniego-Gámez, Erick Maldonado-Bandala, Demetrio Nieves-Mendoza, Javier Olguín-Coca, Jesús Manuel Jáquez-Muñoz, José Cabral-Miramontes, Juan Pablo Flores-De los Rios, Raul German Bautista-Margulis and Citlalli Gaona-Tiburcio
Metals 2022, 12(6), 1033; https://doi.org/10.3390/met12061033 - 17 Jun 2022
Cited by 10 | Viewed by 3364
Abstract
This research aimed to conduct a passive layer state study on martensitic and semi-austenitic precipitation hardening stainless steels (PHSS) passivated in citric acid and nitric acid baths at 49 and 70 °C for 50 and 75 min and subsequently exposed in 5 wt.% [...] Read more.
This research aimed to conduct a passive layer state study on martensitic and semi-austenitic precipitation hardening stainless steels (PHSS) passivated in citric acid and nitric acid baths at 49 and 70 °C for 50 and 75 min and subsequently exposed in 5 wt.% NaCl and 1 wt.% H2SO4 solutions. Corrosion behavior of the passivated material was observed by using potentiodynamic polarization (PP) according to the ASTM G5-11 standard. The microstructural analysis was performed by optical microscopy and scanning electron microscopy (SEM), while the passivated layer was characterized by X-ray photoelectron spectroscopy (XPS). The results indicated that the semi-austenitic-NA-50 min-70 °C sample showed the best corrosion resistance behavior in both solutions. The XPS characterization confirmed that the martensitic and semi-austenitic surface film presented a mixture of chemical compounds, such as Cr2O3 and Fe(OH)O, respectively. Full article
(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)
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18 pages, 4873 KiB  
Article
Analysis of Hydrogen-Assisted Brittle Fracture Using Phase-Field Damage Modelling Considering Hydrogen Enhanced Decohesion Mechanism
by Yunlong Li and Keshi Zhang
Metals 2022, 12(6), 1032; https://doi.org/10.3390/met12061032 - 17 Jun 2022
Cited by 6 | Viewed by 2466
Abstract
This study proposes a hydrogen-assisted fracture analysis methodology considering associated deformation and hydrogen transport inside a phase-field-based formulation. First, the hydrogen transport around a crack tip is calculated, and then the effect of hydrogen enhanced decohesion (HEDE) is modeled by defining the critical [...] Read more.
This study proposes a hydrogen-assisted fracture analysis methodology considering associated deformation and hydrogen transport inside a phase-field-based formulation. First, the hydrogen transport around a crack tip is calculated, and then the effect of hydrogen enhanced decohesion (HEDE) is modeled by defining the critical energy release rate as a function of hydrogen concentration. The proposed method is based on a coupled hydrogen mechanical damage under phase-field and implemented through a user subroutine in ABAQUS software. The test using compact tension (CT) sample is investigated numerically to study the hydrogen embrittlement on 45CrNiMoVA steel. Experimentally, the microstructural fracture presents a mixed brittle fracture mode, consisting of quasi-cleavage (QC) and intergranular (IG) fracture with hydrogen. This fracture mode is consistent with the suggested HEDE mechanism in the model. The simulation results show that hydrogen accumulates at the crack tip where positive hydrostatic stress is located. Moreover, the model estimates the initial hydrogen concentration through iterations. The simulated load-line displacement curves show good agreement with the experimental plots, demonstrating the predictive capabilities of the presented scheme. Full article
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12 pages, 4605 KiB  
Article
Surface Topography Control of TA2 Pure Titanium in Laser Shock Peening
by Wei Cheng, Fengze Dai, Shu Huang, Sergey Konovalov and Xizhang Chen
Metals 2022, 12(6), 1031; https://doi.org/10.3390/met12061031 - 17 Jun 2022
Cited by 4 | Viewed by 1629
Abstract
Laser shock peening (LSP) induces an irregular topography on the treated metal surface, thereby reducing the gain effect of the metal fatigue property caused by compressive residual stress. A technique named laser shock imprinting (LSI) is proposed in this paper to guide plastic [...] Read more.
Laser shock peening (LSP) induces an irregular topography on the treated metal surface, thereby reducing the gain effect of the metal fatigue property caused by compressive residual stress. A technique named laser shock imprinting (LSI) is proposed in this paper to guide plastic deformation on a titanium surface. An FEM simulation and experiment were conducted to explore the embossment forming process and residual stress distribution of TA2 pure titanium. The simulated results show that the embossment on the sample surface went through five stages, namely, static, growth, rebound, fluctuation and stabilization, under a single LSI. With an increase in loading pressure, the contact pressure between the sample and contact foil increased along with increasing embossment height. Sufficient loading pressure could induce a difference in residual stress between the zones with and without embossment. The experimental results show that the height and clarity of embossment increased with increasing laser energy, a result similar to that of the simulation. In addition, compared with LSP, the sample treated by LSI had a lower surface roughness and flatter surface profile. Full article
(This article belongs to the Section Metal Failure Analysis)
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12 pages, 4677 KiB  
Article
Processing of Low-Quality Gibbsite-Kaolinite Bauxites
by Symbat Dyussenova, Rinat Abdulvaliyev, Ata Akcil, Sergey Gladyshev and Galiya Ruzakhunova
Metals 2022, 12(6), 1030; https://doi.org/10.3390/met12061030 - 17 Jun 2022
Cited by 4 | Viewed by 2431
Abstract
The results of studies on the processing of gibbsite-kaolinite bauxite are presented. The developed technology includes preliminary chemical activation and thermal transformation during enrichment to obtain a concentrate suitable for processing by the Bayer method. As a result of the chemical activation of [...] Read more.
The results of studies on the processing of gibbsite-kaolinite bauxite are presented. The developed technology includes preliminary chemical activation and thermal transformation during enrichment to obtain a concentrate suitable for processing by the Bayer method. As a result of the chemical activation of gibbsite-kaolinite bauxite in a solution of sodium bicarbonate, a change in the phase composition occurs, which made it possible to improve the results of gravity enrichment with the production of a coarse-grained gibbsite fraction. The transformation of bauxite in the temperature range of 900–1000 °C is explained by the decomposition reactions of siderite, gibbsite, kaolinite, calcite, dolomite and sodium ferro-sulfide oxide, as well as the formation of sodium aluminosilicate, hematite, quartz and the chemically stable phase of corundum. The optimum firing temperature of bauxite is 950 °C, after which, as a result of alkaline treatment during chemical enrichment, the extraction of SiO2 into solution was 74.9%. A silicon modulus of enriched bauxite 10.9 units was obtained. As a result of the autoclave leaching of gibbsite-kaolinite bauxite after a two-stage enrichment, the maximum extraction of alumina into solution was 87.4%. The yield of red mud during the processing of bauxite enriched and calcined at 950 °C was 37.62%. During the autoclave leaching of bauxite without enrichment, the yield of red mud was 71%. Full article
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13 pages, 6920 KiB  
Article
Effect of Process Control Agent on Microstructures and High-Temperature Oxidation Behavior of a Nickel-Based ODS Alloy
by Zhe Mao, Jing Li, Shi Liu and Liangyin Xiong
Metals 2022, 12(6), 1029; https://doi.org/10.3390/met12061029 - 17 Jun 2022
Viewed by 2195
Abstract
Two nickel-based oxide-dispersion-strengthened (ODS) alloys supplemented with different amounts of process control agent (PCA) were prepared. The microstructures including grains and nanometric oxides and the subsequent oxidation behavior of these ODS alloys were investigated. It was found that the distribution of nanometric oxides [...] Read more.
Two nickel-based oxide-dispersion-strengthened (ODS) alloys supplemented with different amounts of process control agent (PCA) were prepared. The microstructures including grains and nanometric oxides and the subsequent oxidation behavior of these ODS alloys were investigated. It was found that the distribution of nanometric oxides in the nickel-based ODS alloy is uniform and the grains are refined by adding a proper amount of PCA in the mechanical milling, while the blocking effect on the diffusion of active elements Y, Al and Ti among powders takes place with an excessive amount of PCA, resulting in the precipitation of large-size oxides in local areas of the alloy. After oxidation in air at 1000 °C for 200 h, the oxide scales on the surface of both nickel-based ODS alloys are composed of Cr2O3. As Y-rich oxide particles are precipitated in the matrix, the thickness of the oxide scale is significantly reduced compared with non-ODS alloys. However, due to the influence of grain boundaries on the diffusion of elements, the oxide scale on the surface of an alloy with finer grain size is thicker. The oxidation resistance of ODS alloys strongly depends on the exact manufacturing process. Full article
(This article belongs to the Special Issue High Temperature Corrosion or Oxidation of Metals and Alloys)
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16 pages, 26270 KiB  
Article
A Tribological Study on the Effect of Reinforcing SiC and Al2O3 in Al7075: Applications for Spur Gears
by Shridhar H. Budapanahalli, Shekhar B. Mallur, Arun Y. Patil, Abeer Mohamed Alosaimi, Anish Khan, Mahmoud Ali Hussein and Abdullah M. Asiri
Metals 2022, 12(6), 1028; https://doi.org/10.3390/met12061028 - 17 Jun 2022
Cited by 13 | Viewed by 2642
Abstract
In today’s world, efficiency and margin of safety are prime considerations for any applications. To address such parameters in aerospace or high-tech consumer products, there are still limitations in terms of capabilities from a material perspective. Aluminium 7075 is predominantly used as a [...] Read more.
In today’s world, efficiency and margin of safety are prime considerations for any applications. To address such parameters in aerospace or high-tech consumer products, there are still limitations in terms of capabilities from a material perspective. Aluminium 7075 is predominantly used as a combination material in these applications, but it has many drawbacks such as early wear/friction, low fatigue life cycle, high weight ratios, high deformation and stresses. To overcome these key issues, many reinforcements have been used to date. However, the results are not so convincing with respect to tribological applications, and the aforementioned issues still persist. In the current work, a novel hybrid composite comprising Aluminium 7075 as substrate and the reinforcement of silicon carbide and aluminium oxide at varying combinations of 3 to 9% in steps of 3% and a constant percentage of 5% were added, respectively. The exhaustive work focuses on extracting the mechanical, tribological and physical properties of a hybrid composite. Furthermore, a microcharacterisation study of these combinations was carried out using FE-SEM and EDX. In a continuation to this simulation, a study was performed using ANSYS Workbench to identify a suitable gear application with real-time loading conditions. The observed results show a tensile strength of 366 MPa for 6%SiC, hardness of 93 VHN and wear rate of 0.00025 mm3/Nm for the 9%SiC combination. Full article
(This article belongs to the Topic Metal Matrix Composites: Recent Advancements)
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