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5 pages, 179 KiB

Open AccessEditorial

Strengthening Mechanisms in Metallic Materials

by Andrii G. Kostryzhev

Metals 2021, 11(7), 1134; https://doi.org/10.3390/met11071134 - 18 Jul 2021

Cited by 7 | Viewed by 3946

Abstract

The mechanical properties of contemporary engineering alloys are approaching their natural limits [...] Full article

(This article belongs to the Special Issue Strengthening Mechanisms in Metallic Materials)

Research

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19 pages, 6166 KiB

Open AccessArticle

Synthesis of Functional Surface Layers on Stainless Steels by Laser Alloying

by Zoia Duriagina, Volodymyr Kulyk, Taras Kovbasiuk, Bogdan Vasyliv and Andrii Kostryzhev

Metals 2021, 11(3), 434; https://doi.org/10.3390/met11030434 - 6 Mar 2021

Cited by 28 | Viewed by 2559

Abstract

Laser alloying is an effective method to form functional surface layers (coatings) on metallic materials, particularly on stainless steels. Unique phase balance, dislocation substructure, and a possibility to obtain gradient microstructures after laser alloying slow down the surface degradation and increase the wear [...] Read more.

Laser alloying is an effective method to form functional surface layers (coatings) on metallic materials, particularly on stainless steels. Unique phase balance, dislocation substructure, and a possibility to obtain gradient microstructures after laser alloying slow down the surface degradation and increase the wear resistance. In this work, the optimal parameters of laser alloying and their effects on microstructure and properties were investigated for two stainless steels: ferritic AISI 420 and austenitic AISI 304. Three types of alloying plasters were used: 85Nb + 15 graphite, 85Nb + 15 liquid glass, and 15Fe + 30Ni + 20B + 10Si + 25 liquid glass (wt.%). The laser power density of 0.3 × 10⁵ W/cm² and beam scanning speed of 1990 mm/min were found to generate 220–320 μm thick coatings with complex microstructures. Phase balance in the coatings was studied with X-ray diffraction and magnetometric phase analyses. High microhardness (up to 16 GPa) and wear resistance were associated with the formation of martensite with some retained austenite and Nb-, Cr-, Si-, and B-rich particles in the surface layer of AISI 420 steel, and high dislocation density austenite strengthened with Ti-, Nb-, Cr-, and Si-rich particles in AISI 304 steel. Full article

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12 pages, 7828 KiB

Open AccessArticle

Characterization of Sintered Aluminium Reinforced with Ultrafine Tungsten Carbide Particles

by Omid Emadinia, Maria Teresa Vieira and Manuel Fernando Vieira

Metals 2020, 10(11), 1416; https://doi.org/10.3390/met10111416 - 25 Oct 2020

Cited by 2 | Viewed by 2041

Abstract

The strengthening effect on aluminium (Al) by ultrafine particles of tungsten carbide (WC) after compacting and sintering was evaluated. The Al-1 vol.% WC mixture was prepared through a high-speed stirring technique, called assisted sonication. In this study, the effects of compacting, sintering temperature [...] Read more.

The strengthening effect on aluminium (Al) by ultrafine particles of tungsten carbide (WC) after compacting and sintering was evaluated. The Al-1 vol.% WC mixture was prepared through a high-speed stirring technique, called assisted sonication. In this study, the effects of compacting, sintering temperature and holding time were evaluated by composite microstructural characterization and by mechanical tests. The characterizations involved electron dispersive spectroscopy and X-ray diffraction techniques for phase identification; electron backscattered diffraction for crystallographic analysis; backscattered electrons and secondary electrons imaging for failure and wear studies. In all composites, hardness was determined; for the hardest composite, the tensile strength, flexural strength and ball scattering wear resistance were also evaluated. The Al-1 vol.% WC composite produced by assisted sonication, densified by cold compacting at 152 MPa and sintered at 640 °C for 2 h at 5 × 10⁻⁴ Pa (high vacuum) exhibited the highest hardness, associated with an acceptable ductile behavior. This strengthening was associated with the formation of Al₁₂W and grain refinement. Full article

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11 pages, 5148 KiB

Open AccessArticle

In Situ Synchrotron X-ray Study of the Mechanical Properties of Pure Mg Produced by Powder Metallurgy

by Li Li, Leyun Wang, Jie Wang, Huan Zhang, Qingchun Zhu, Zhiqiang Li and Xiaoqin Zeng

Metals 2020, 10(9), 1198; https://doi.org/10.3390/met10091198 - 8 Sep 2020

Cited by 4 | Viewed by 2988

Abstract

In this study, in situ synchrotron X-ray experiments with wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) detectors were performed on two pure magnesium materials produced by powder metallurgy. According to SAXS analysis, each of the two materials has a porosity of [...] Read more.

In this study, in situ synchrotron X-ray experiments with wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) detectors were performed on two pure magnesium materials produced by powder metallurgy. According to SAXS analysis, each of the two materials has a porosity of less than 0.5%. Line broadening analysis was performed on diffraction patterns collected by WAXS to analyze the dislocation evolution during material deformation. In both materials, <a>-type dislocation activities dominate the tensile deformation. The influence of grain size and texture on the different tensile behaviors of these two materials is also discussed. Full article

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15 pages, 14873 KiB

Open AccessArticle

New Twin-Roll Cast Al-Li Based Alloys for High-Strength Applications

by Olexandr Grydin, Mykhailo Stolbchenko, Mirko Schaper, Sára Belejová, Rostislav Králík, Lucia Bajtošová, Barbora Křivská, Michal Hájek and Miroslav Cieslar

Metals 2020, 10(8), 987; https://doi.org/10.3390/met10080987 - 22 Jul 2020

Cited by 14 | Viewed by 3120

Abstract

Al-Li based alloys are attractive materials for the aerospace industry. The twin-roll casting of such materials could provide properties not achievable by conventional direct-chill casting and downstream processing methods due to significantly higher solidification rates. An Al-Li-Cu-Mg-Zr alloy was twin-roll cast with the [...] Read more.

Al-Li based alloys are attractive materials for the aerospace industry. The twin-roll casting of such materials could provide properties not achievable by conventional direct-chill casting and downstream processing methods due to significantly higher solidification rates. An Al-Li-Cu-Mg-Zr alloy was twin-roll cast with the same alloy containing a small addition of Sc. The microstructure of as-cast materials and the influence of Sc on the behavior of the alloy at elevated temperatures were studied by means of light and electron microscopy and by resistivity measurements. A fine-grained structure was formed during twin-roll casting, but several surface and internal defects were found on the strips, which should be suppressed by a further adjustment of the casting conditions. The addition of Sc had a positive effect on grain size uniformity and microstructure stabilization at elevated temperatures, as shown by the precipitation of a fine dispersion of coherent Sc- and Zr-containing precipitates. Full article

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14 pages, 5555 KiB

Open AccessArticle

Initial Deformation Behaviors in Lean Duplex Stainless Steel

by Rosa Kim, Cheoljun Bae and Jongryoul Kim

Metals 2020, 10(7), 936; https://doi.org/10.3390/met10070936 - 11 Jul 2020

Cited by 4 | Viewed by 2806

Abstract

The deformation behaviors of the austenite phase in lean duplex stainless steels were investigated through uniaxial tension tests with different amounts of deformation. Microstructural analysis showed that in the initial deformation stage the deformation in austenite grains had a predominant effect on the [...] Read more.

The deformation behaviors of the austenite phase in lean duplex stainless steels were investigated through uniaxial tension tests with different amounts of deformation. Microstructural analysis showed that in the initial deformation stage the deformation in austenite grains had a predominant effect on the strain hardening behavior of the LDX-2101 steel. The initial deformation in the austenite grains was found to be mainly accommodated by the formation of stacking faults. As the deformation increased further, mechanical twins were generated by the initial stacking faults and sequentially interacted with dislocations to accommodate the strain. The analysis of dislocation behavior revealed that the deformation twinning process followed the three-layer twin formation mechanism. Full article

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13 pages, 4732 KiB

Open AccessArticle

Analysis of the Bauschinger Effect in Cold Drawn Pearlitic Steels

by Jesús Toribio, Viktor Kharin, Francisco-Javier Ayaso, Miguel Lorenzo, Beatriz González, Juan-Carlos Matos and Leticia Aguado

Metals 2020, 10(1), 114; https://doi.org/10.3390/met10010114 - 12 Jan 2020

Cited by 11 | Viewed by 6526

Abstract

Prestressing steel wires usually undergo cyclic loading in service. Therefore, it is of interest to analyse certain features of their mechanical behaviour under this type of loading, such as the Bauschinger effect (BE) or the hardening rule, that fit the real mechanical behaviour [...] Read more.

Prestressing steel wires usually undergo cyclic loading in service. Therefore, it is of interest to analyse certain features of their mechanical behaviour under this type of loading, such as the Bauschinger effect (BE) or the hardening rule, that fit the real mechanical behaviour appropriately. In this study, different samples of high strength pearlitic steel wires were subjected to cyclic tension-compression load exceeding the material yield strength, thus generating plastic strains. From the experimental results, various parameters were obtained revealing that analysed steels exhibited the so-called Masing type BE. In addition, the variation of the BE characteristics (of the effective and internal stresses) with the applied plastic pre-strain indicated that the studied materials followed a mixed strain hardening rule with the domination of the kinematic component. Full article

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7 pages, 3428 KiB

Open AccessArticle

Production of Surface Layer with Gradient Microstructure and Microhardess on Copper by High Pressure Surface Rolling

by Juying Li, Qingsong Mei, Yana Li and Beihai Wang

Metals 2020, 10(1), 73; https://doi.org/10.3390/met10010073 - 2 Jan 2020

Cited by 16 | Viewed by 2390

Abstract

Pure copper was subjected to high-pressure surface rolling (HPSR) to obtain a surface gradient layer. Effects of HPSR parameters on the surface microstructure and microhardness of Cu were investigated by using optical microscopy, transmission electronic microscopy, X-ray diffraction, and the microhardness test. The [...] Read more.

Pure copper was subjected to high-pressure surface rolling (HPSR) to obtain a surface gradient layer. Effects of HPSR parameters on the surface microstructure and microhardness of Cu were investigated by using optical microscopy, transmission electronic microscopy, X-ray diffraction, and the microhardness test. The HPSR surface layer has a gradient microstructure consisting of increasingly refined grains with decreasing depth from the treated surface (DFS). The thicknesses of the refined surface layer can be up to ~1.8 mm, and the grain size of the topmost surface is down to ~88 nm, depending on the HPSR parameters including pressure, time, and temperature. Microhardness of HPSR samples increases with decreasing DFS, with a maximum of ~2.4 times that of the undeformed matrix. The present results indicated that HPSR could be an effective method for the production of a mm-thick surface layer on Cu with gradient microstructure and property. Full article

(This article belongs to the Special Issue Strengthening Mechanisms in Metallic Materials)

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17 pages, 4863 KiB

Open AccessArticle

Influence of Tempering Time on the Behavior of Large Carbides’ Coarsening in AISI H13 Steel

by Angang Ning, Stephen Yue, Rui Gao, Lingxia Li and Hanjie Guo

Metals 2019, 9(12), 1283; https://doi.org/10.3390/met9121283 - 29 Nov 2019

Cited by 14 | Viewed by 4064

Abstract

The mechanical properties, microstructures and precipitation behaviors in AISI (American Iron and Steel Institute) H13 steel tempered at 863 K for 0.5, 2, 4, 10 and 20 h were investigated. The values for H13 tempered for 2–4 h resulted in die steel that [...] Read more.

The mechanical properties, microstructures and precipitation behaviors in AISI (American Iron and Steel Institute) H13 steel tempered at 863 K for 0.5, 2, 4, 10 and 20 h were investigated. The values for H13 tempered for 2–4 h resulted in die steel that reached the desired properties as specified in NADCA (North American Die Casting Association) #207-2016. The cubic Ostwald ripening model was applied to simulate the coarsening of the large carbides, which were mainly M₂₃C₆ and M₃C, as determined from FactSage predictions as well as measurements with transmission electron microscopy (TEM). TEM revealed that the equivalent circle radius (ECR) decreased during 0.5–2 h, because of the nucleation of many new precipitates. According to the Ashby-Orowan modified precipitation strengthening model, this decrease in ECR leads to an increase in the contribution of precipitates to yield strength. Between 2 and 4 h tempering, the ECR of large carbides increases sharply but then increases asymptotically from 4 to 20 h, which obeys the calculated Ostwald ripening rate for cementite and M₂₃C₆ in H13 after 863 K tempering. This observation for the Ostwald ripening of M₂₃C₆ is in agreement with experimental data for other steels in the literature. Full article

(This article belongs to the Special Issue Strengthening Mechanisms in Metallic Materials)

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18 pages, 4284 KiB

Open AccessArticle

Effect of Strengthening Methods on the Defect Evolution under Irradiations Investigated with Rate Theory Simulations

by Cheng Chen, Liping Guo, Yaxia Wei, Ziyang Xie and Yunxiang Long

Metals 2019, 9(7), 735; https://doi.org/10.3390/met9070735 - 29 Jun 2019

Cited by 6 | Viewed by 3079

Abstract

Under irradiations, mechanical performance of nuclear alloys would degrade due to irradiation induced defects. Different strengthening methods can play a different role in the evolution of the defects. In this study, the effect of four typical strengthening methods including fine grain strengthening, dislocation [...] Read more.

Under irradiations, mechanical performance of nuclear alloys would degrade due to irradiation induced defects. Different strengthening methods can play a different role in the evolution of the defects. In this study, the effect of four typical strengthening methods including fine grain strengthening, dislocation strengthening, second phase strengthening and solid solutions strengthening on the defect evolutions in bcc iron-based alloys are investigated with rate theory simulations, a technique capable of simulating a long-term evolution of defects caused by irradiations. Simulations show that at high dose, irradiation induced voids become the dominating factor that affect irradiation hardening. Strengthening methods with the enhancement of sink strength (fine grain strengthening, dislocation strengthening and second phase strengthening) have little effects on the evolution of voids, while strengthening method with impediment of migration of defects (solid solutions strengthening) can effectively inhibit the nucleation and growth of voids. For fine grain strengthening and dislocation strengthening, the irradiation hardening is almost kept unchanged when changing grain size and initial dislocation density. For second phase strengthening, the irradiation hardening can be inhibited to some extent by increasing mainly the number density of precipitates. The solid solutions strengthening is the most proper method to inhibit irradiation hardening of bcc iron-based alloy because it can inhibit the development of voids, especially at high dose. Full article

(This article belongs to the Special Issue Strengthening Mechanisms in Metallic Materials)

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14 pages, 5571 KiB

Open AccessArticle

Precipitation Strengthening in Ni–Cu Alloys Fabricated Using Wire Arc Additive Manufacturing Technology

by Olexandra Marenych, Andrii Kostryzhev, Chen Shen, Zengxi Pan, Huijun Li and Stephen van Duin

Metals 2019, 9(1), 105; https://doi.org/10.3390/met9010105 - 21 Jan 2019

Cited by 20 | Viewed by 5192

Abstract

Two Ni–Cu alloys, Monel K500 and FM60, with various contents of Ti, Mn, Al, Fe and C were deposited in the form of plates on a metal base plate using wire arc additive manufacturing technology. Three deposition speeds have been applied: 300, 400 [...] Read more.

Two Ni–Cu alloys, Monel K500 and FM60, with various contents of Ti, Mn, Al, Fe and C were deposited in the form of plates on a metal base plate using wire arc additive manufacturing technology. Three deposition speeds have been applied: 300, 400 and 500 mm/min. To modify the as-welded microstructure and properties, the deposited walls/plates have been subjected to two heat treatment procedures: annealing at 1100 °C for 15 min, slow cooling to 610 °C, ageing at this temperature for 8 h and either (i) air cooling to room temperature or (ii) slow cooling to 480 °C, ageing at this temperature for 8 h and air cooling to room temperature. The microstructure characterisation and mechanical properties testing have been conducted for each of the 18 chemistry/processing conditions. The dependences of the precipitate’s parameters (size, number density and chemistry), mechanical properties and wear resistance on the alloy composition, deposition speed and heat treatment have been obtained. In Monel K500, the precipitates were mainly of the TiC/TiCN type, and in FM60, they were of the MnS and TiAlMgO types. Monel K500 has shown higher hardness, strength, toughness and wear resistance in all studied conditions. Ageing at 610 °C improved properties in both alloys following the precipitation of new particles. Ageing at 480 °C could result in a properties loss if the particle coarsening (decrease in number density) took place. Full article

(This article belongs to the Special Issue Strengthening Mechanisms in Metallic Materials)

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12 pages, 4327 KiB

Open AccessArticle

Effect of T6 Heat Treatment on Microstructure and Hardness of Nanosized Al₂O₃ Reinforced 7075 Aluminum Matrix Composites

by Peng-Xiang Zhang, Hong Yan, Wei Liu, Xiu-Liang Zou and Bin-Bing Tang

Metals 2019, 9(1), 44; https://doi.org/10.3390/met9010044 - 5 Jan 2019

Cited by 34 | Viewed by 5479

Abstract

In this study, 7075 aluminum matrix composites reinforced with 1.5 wt.% nanosized Al₂O₃ were fabricated by ultrasonic vibration. The effect of T6 heat treatment on both microstructure and hardness of nanosized Al₂O₃ reinforced 7075 (Al₂O [...] Read more.

In this study, 7075 aluminum matrix composites reinforced with 1.5 wt.% nanosized Al₂O₃ were fabricated by ultrasonic vibration. The effect of T6 heat treatment on both microstructure and hardness of nanosized Al₂O₃ reinforced 7075 (Al₂O_3np/7075) composites were studied via scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, transmission electron microscopy, and hardness tests. The Mg(Zn,Cu,Al)₂ phases gradually dissolved into the matrix under solution treatment at 480 °C for 5 h. However, the morphology and size of Al₇Cu₂Fe phases remained unchanged due to their high melting points. Furthermore, the slenderness strips MgZn₂ phases precipitated under aging treatment at 120 °C for 24 h. Compared to as-cast composites, the hardness of the sample under T6 heat treatment was increased ~52%. The strengthening mechanisms underlying the achieved hardness of composites are revealed. Full article

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14 pages, 12626 KiB

Open AccessArticle

Microstructure, Mechanical Properties and Strengthening Mechanism Analysis in an AlMg5 Aluminium Alloy Processed by ECAP and Subsequent Ageing

by Przemysław Snopiński and Mariusz Król

Metals 2018, 8(11), 969; https://doi.org/10.3390/met8110969 - 20 Nov 2018

Cited by 17 | Viewed by 4140

Abstract

A coarse-grained microstructure of solution treated AlMg5 aluminium alloy was prepared by equal channel angular pressing through route B_C. Microstructure evolution of the alloy was analysed by using an optical microscope, X-ray diffraction, and EBSD (electron backscatter diffraction). The results reported [...] Read more.

A coarse-grained microstructure of solution treated AlMg5 aluminium alloy was prepared by equal channel angular pressing through route B_C. Microstructure evolution of the alloy was analysed by using an optical microscope, X-ray diffraction, and EBSD (electron backscatter diffraction). The results reported that grains were refined due to the interactions of shear bands with low-to-moderate grain boundaries, and this structure was transformed into a bimodal after ageing at 180 °C for 4 h. Moreover, the results of the tensile testing showed that the yield strength was increased from 110 to 326 MPa, and the corresponding tensile strength increased from 269 to 395 MPa, maintaining an appropriate elongation of ~18%. After ageing at 180 °C elongation increased to 23% and the sample still kept high yield strength of 255 MPa, which may be associated with the mutual influence of the dislocation density decrease and recrystallization processes. Full article

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18 pages, 6853 KiB

Open AccessFeature PaperReview

Strengthening Mechanisms in Nickel-Copper Alloys: A Review

by Olexandra Marenych and Andrii Kostryzhev

Metals 2020, 10(10), 1358; https://doi.org/10.3390/met10101358 - 12 Oct 2020

Cited by 52 | Viewed by 14105

Abstract

Nickel-Copper (Ni-Cu) alloys exhibit simultaneously high strength and toughness, excellent corrosion resistance, and may show good wear resistance. Therefore, they are widely used in the chemical, oil, and marine industries for manufacturing of various components of equipment, such as: drill collars, pumps, valves, [...] Read more.

Nickel-Copper (Ni-Cu) alloys exhibit simultaneously high strength and toughness, excellent corrosion resistance, and may show good wear resistance. Therefore, they are widely used in the chemical, oil, and marine industries for manufacturing of various components of equipment, such as: drill collars, pumps, valves, impellers, fixtures, pipes, and, particularly, propeller shafts of marine vessels. Processing technology includes bar forging, plate and tube rolling, wire drawing followed by heat treatment (for certain alloy compositions). Growing demand for properties improvement at a reduced cost initiate developments of new alloy chemistries and processing technologies, which require a revision of the microstructure-properties relationship. This work is dedicate to analysis of publicly available data for the microstructure, mechanical properties and strengthening mechanisms in Ni-Cu alloys. The effects of composition (Ti, Al, Mn, Cr, Mo, Co contents) and heat treatment on grain refinement, solid solution, precipitation strengthening, and work hardening are discussed. Full article

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32 pages, 9799 KiB

Open AccessReview

A Review on Heterogeneous Nanostructures: A Strategy for Superior Mechanical Properties in Metals

by Yan Ma, Muxin Yang, Fuping Yuan and Xiaolei Wu

Metals 2019, 9(5), 598; https://doi.org/10.3390/met9050598 - 24 May 2019

Cited by 51 | Viewed by 6936

Abstract

Generally, strength and ductility are mutually exclusive in homogeneous metals. Nanostructured metals can have much higher strength when compared to their coarse-grained counterparts, while simple microstructure refinement to nanoscale generally results in poor strain hardening and limited ductility. In recent years, heterogeneous nanostructures [...] Read more.

Generally, strength and ductility are mutually exclusive in homogeneous metals. Nanostructured metals can have much higher strength when compared to their coarse-grained counterparts, while simple microstructure refinement to nanoscale generally results in poor strain hardening and limited ductility. In recent years, heterogeneous nanostructures in metals have been proven to be a new strategy to achieve unprecedented mechanical properties that are not accessible to their homogeneous counterparts. Here, we review recent advances in overcoming this strength–ductility trade-off by the designs of several heterogeneous nanostructures in metals: heterogeneous grain/lamellar/phase structures, gradient structure, nanotwinned structure and structure with nanoprecipitates. These structural heterogeneities can induce stress/strain partitioning between domains with dramatically different strengths, strain gradients and geometrically necessary dislocations near domain interfaces, and back-stress strengthening/hardening for high strength and large ductility. This review also provides the guideline for optimizing the mechanical properties in heterogeneous nanostructures by highlighting future challenges and opportunities. Full article

(This article belongs to the Special Issue Strengthening Mechanisms in Metallic Materials)

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