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14 pages, 12930 KiB

Open AccessArticle

Evolution of Microstructure and Texture in Grain-Oriented 6.5% Si Steel Processed by Rolling with Intrinsic Inhibitors and Additional Inhibitors

by Ruiyang Liang, Chengqian Sun and Qingchun Li

Materials 2023, 16(20), 6731; https://doi.org/10.3390/ma16206731 - 17 Oct 2023

Viewed by 930

Abstract

A grain-oriented steel containing 6.5% Si, characterized by a notable Goss texture, was effectively manufactured through the rolling technique, incorporating both intrinsic inhibitors and additional inhibitors. This investigation focuses on tracking the development of texture and magnetic properties during the manufacturing process and [...] Read more.

A grain-oriented steel containing 6.5% Si, characterized by a notable Goss texture, was effectively manufactured through the rolling technique, incorporating both intrinsic inhibitors and additional inhibitors. This investigation focuses on tracking the development of texture and magnetic properties during the manufacturing process and delineates the mechanism underlying secondary recrystallization. The empirical findings clearly demonstrated the significant influence of nitriding duration and quantity on the secondary recrystallization process. In instances where additional nitrogen is absent, the intrinsic inhibitors alone do not lead to secondary recrystallization. However, when the nitriding duration is 90 s and the nitriding amount is 185 ppm, a complete secondary recrystallization structure with a strong Goss texture enables the finished products have excellent magnetic properties. The preferential growth of Goss grains is mainly governed by the enhanced mobility of high-energy (HE) grain boundaries. With the increase in annealing temperature, the occurrence of 20°–45° HE grain boundaries with Goss grains becomes more progressively frequent. At the secondary recrystallization temperature of 1000 °C, the frequency of 20°–45° HE grain boundaries with Goss grains reaches 62.7%, providing favorable conditions for the abnormal growth of Goss grains. This results in a secondary recrystallization structure predominantly characterized by a strong Goss texture. In light of these observations, the present study provides fundamental theoretical insights and serves as a valuable procedural guideline for the industrial manufacturing of 6.5% Si grain-oriented electrical steels. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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19 pages, 6114 KiB

Open AccessEditor’s ChoiceArticle

3D Model of Heat Flow during Diffusional Phase Transformations

by Łukasz Łach and Dmytro Svyetlichnyy

Materials 2023, 16(13), 4865; https://doi.org/10.3390/ma16134865 - 6 Jul 2023

Cited by 2 | Viewed by 1299

Abstract

The structure of metallic materials has a significant impact on their properties. One of the most popular methods to form the properties of metal alloys is heat treatment, which uses thermally activated transformations that take place in metals to achieve the required mechanical [...] Read more.

The structure of metallic materials has a significant impact on their properties. One of the most popular methods to form the properties of metal alloys is heat treatment, which uses thermally activated transformations that take place in metals to achieve the required mechanical or physicochemical properties. The phase transformation in steel results from the fact that one state becomes less durable than the other due to a change in conditions, for example, temperature. Phase transformations are an extensive field of research that is developing very dynamically both in the sphere of experimental and model research. The objective of this paper is the development of a 3D heat flow model to model heat transfer during diffusional phase transformations in carbon steels. This model considers the two main factors that influence the transformation: the temperature and the enthalpy of transformation. The proposed model is based on the lattice Boltzmann method (LBM) and uses CUDA parallel computations. The developed heat flow model is directly related to the microstructure evolution model, which is based on frontal cellular automata (FCA). This paper briefly presents information on the FCA, LBM, CUDA, and diffusional phase transformation in carbon steels. The structures of the 3D model of heat flow and their connection with the microstructure evolution model as well as the algorithm for simulation of heat transfer with consideration of the enthalpy of transformation are shown. Examples of simulation results of the growth of the new phase that are determined by the overheating/overcooling and different model parameters in the selected planes of the 3D calculation domain are also presented. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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12 pages, 5384 KiB

Open AccessArticle

Effect of Sintering Temperature and Iron Addition on Properties and Microstructure of High Speed Steel Based Materials Produced by Spark Plasma Sintering Method

by Marcin Madej, Beata Leszczyńska-Madej and Dariusz Garbiec

Materials 2022, 15(21), 7607; https://doi.org/10.3390/ma15217607 - 29 Oct 2022

Cited by 3 | Viewed by 1553

Abstract

Attempts were made to describe the effect of the sintering temperature and pure iron powder addition on the properties of HSS-based materials produced by the spark plasma sintering method (SPS). After sintering, their density, hardness, flexural strength, and tribological properties were determined. The [...] Read more.

Attempts were made to describe the effect of the sintering temperature and pure iron powder addition on the properties of HSS-based materials produced by the spark plasma sintering method (SPS). After sintering, their density, hardness, flexural strength, and tribological properties were determined. The sintered materials were also subjected to microstructural analysis to determine the phenomena occurring at the particle contact boundaries during sintering. On the basis of analysis of the obtained results, it was found that the mechanical properties and microstructure were mainly influenced by the sintering temperature, which was selected in relation to the previously tested steel M3/2, adjusted upwards due to its chemical composition. The use of the temperature of 1050 °C allows materials to be obtained with a density close to the theoretical density (97%), characterized by a high hardness of about 360 HB. The addition of iron slightly reduces the hardness and also increases the flexural strength to 577 MPa. There was no diffusion of the alloying elements from the steel to the iron due to the short time of exposure to the sintering temperature. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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20 pages, 10397 KiB

Open AccessArticle

Effect of Cold Rolling on Microstructural and Mechanical Properties of a Dual-Phase Steel for Automotive Field

by Emilio Bassini, Giulio Marchese, Antonio Sivo, Pietro Antonio Martelli, Alessio Gullino and Daniele Ugues

Materials 2022, 15(21), 7482; https://doi.org/10.3390/ma15217482 - 25 Oct 2022

Cited by 7 | Viewed by 2137

Abstract

A new advanced dual-phase (DP) steel characterized by ferrite and bainite presence in equal fractions has been studied within this paper. The anisotropy change of this steel was assessed as a progressively more severe cold rolling process was introduced. Specifically, tensile tests were [...] Read more.

A new advanced dual-phase (DP) steel characterized by ferrite and bainite presence in equal fractions has been studied within this paper. The anisotropy change of this steel was assessed as a progressively more severe cold rolling process was introduced. Specifically, tensile tests were used to build a strain-hardening curve, which describes the evolution of this DP steel’s mechanical properties as the thinning level increases from 20 to 70% with 10% step increments. As expected, the cold rolling process increases mechanical properties, profoundly altering the material’s microstructure, which was assessed in depth using Electron Backscatter Diffraction (EBSD) analysis coupled with the Kernel Average Misorientation (KAM) maps. At the same time, the process strongly modifies the material planar anisotropy. Microstructural and mechanical assessment and the Kocks–Mecking model applied to this steel evidenced that a 50% strain hardening makes the DP steel isotropic. The material retains or resumes anisotropic behavior for a lower or higher degree of deformation. Furthermore, the paper evaluated the forming limit of this DP steel and introduced geometric limitations to testing the thin steel plates’ mechanical properties. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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19 pages, 6369 KiB

Open AccessArticle

Microstructural Characterization of Additively Manufactured Metal Components Using Linear and Nonlinear Ultrasonic Techniques

by Seong-Hyun Park, Sungho Choi, Dong-Gi Song and Kyung-Young Jhang

Materials 2022, 15(11), 3876; https://doi.org/10.3390/ma15113876 - 29 May 2022

Cited by 20 | Viewed by 2830

Abstract

Metal additive manufacturing (AM) is an innovative manufacturing technology that uses a high-power laser for the layer-by-layer production of metal components. Despite many achievements in the field of AM, few studies have focused on the nondestructive characterization of microstructures, such as grain size [...] Read more.

Metal additive manufacturing (AM) is an innovative manufacturing technology that uses a high-power laser for the layer-by-layer production of metal components. Despite many achievements in the field of AM, few studies have focused on the nondestructive characterization of microstructures, such as grain size and porosity. In this study, various microstructures of additively manufactured metal components were characterized non-destructively using linear/nonlinear ultrasonic techniques. The contributions of this study are as follows: (1) presenting correlation analyses of various microstructures (grain size and texture, lack of fusion, and porosity) and ultrasonic properties (ultrasonic velocity, attenuation, and nonlinearity parameters), (2) development of nondestructive microstructural characterization techniques for additively manufactured components; and (3) exploring the potential for the online monitoring of AM processes owing to the nondestructive nature of the proposed technique. The performance of the proposed technique was validated using additively manufactured samples under varying laser beam speed conditions. The characteristics of the target microstructures characterized using the proposed technique were consistent with the results obtained using destructive optical microscopy and electron back-scattered diffraction methods. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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19 pages, 20819 KiB

Open AccessArticle

In Situ Tensile Deformation and Mechanical Properties of α Platelets TC21 Alloy

by Chunlin Yang, Song Zhang and Meigui Ou

Materials 2022, 15(11), 3869; https://doi.org/10.3390/ma15113869 - 28 May 2022

Viewed by 2024

Abstract

The present study was focused on the relationship between an α platelet microstructure and the properties of TC21 alloy, and the tensile deformation process was revealed by in situ observation. To obtain the α platelet microstructures, the samples were administered a solution treatment [...] Read more.

The present study was focused on the relationship between an α platelet microstructure and the properties of TC21 alloy, and the tensile deformation process was revealed by in situ observation. To obtain the α platelet microstructures, the samples were administered a solution treatment (1000 °C for 15 min) and then cooled to room temperature by different cooling methods (furnace cooling (FC), open-door furnace cooling (OFC), air cooling (AC), and water quench (WQ), corresponding to an increased cooling rate). It is found that α platelets become thinner and colonies become narrower with the increase in cooling rate. The formation of the platelet microstructure is based on the preferred Burgers orientation relationship of {110}_β//{0001}_α and <111>_β//<11

\bar{2}

0>_α. The α platelets orientation changes with the cooling rate. These differences in α platelets thickness and orientation result in the excellent ductility of the sample with thick platelets and the high strength of the samples with thin platelets. During the in situ tensile deformation process, the crack propagation path is deflected in the presence of grain boundaries, α platelets, and α colonies with different orientations. The fracture of the sample with thick α platelets shows better ductility compared to those with thin α platelets. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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17 pages, 16246 KiB

Open AccessArticle

Effect of Multidirectional Isothermal Forging on Microstructure and Mechanical Properties in Ti-6Al-4V Alloy

by Zhichao Xu, Wenju Yang, Jianfeng Fan, Tao Wu and Zeng Gao

Materials 2022, 15(9), 3156; https://doi.org/10.3390/ma15093156 - 27 Apr 2022

Cited by 3 | Viewed by 1832

Abstract

In the present work, the microstructure and mechanical properties of Ti-6Al-4V alloy during multidirectional isothermal forging (MDIF) were systematically investigated. The evolution of the microstructure and texture of Ti-6Al-4V alloy during MDIF was studied using TEM and electron backscattered diffraction (EBSD). The experiment [...] Read more.

In the present work, the microstructure and mechanical properties of Ti-6Al-4V alloy during multidirectional isothermal forging (MDIF) were systematically investigated. The evolution of the microstructure and texture of Ti-6Al-4V alloy during MDIF was studied using TEM and electron backscattered diffraction (EBSD). The experiment results showed that the grain size decreased with the increase in cumulative strain, especially in the easy deformation zone. After four deformation cycles, a homogeneous equiaxed grained microstructure with an average grain size of 0.14 μm was achieved. The texture changes of the alloy were studied in detail. After one cycle of MDIF, the texture was mainly composed of (0002) [01 10], and the Euler angles were (8°, 30°, 30°). The density of texture decreased with the increase in loading cycle, but the dispersion of texture increased. After four cycles of MDIF, the non-basal texture (1010) <1102> texture was observed, and the Euler angles were (82°, 33°, 0°). The highest achieved mechanical properties for Ti-6Al-4V alloy in the MDIF condition were a yield strength 900 MPa, ultimate tensile strength of 921 MPa, and an elongation of 12.1% at room temperature. The increase in MDIF cycles improved the hardness of the alloy. The significant improvement in mechanical properties was attributed to the ultrafine-grained microstructure. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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21 pages, 4611 KiB

Open AccessArticle

Microstructure Evolution and Mechanical Properties of As-Cast and As-Compressed ZM6 Magnesium Alloys during the Two-Stage Aging Treatment Process

by Jia Fu and Su Chen

Materials 2021, 14(24), 7760; https://doi.org/10.3390/ma14247760 - 15 Dec 2021

Cited by 2 | Viewed by 2405

Abstract

In the present study, different solid solution and aging processes of as-cast and as-compressed ZM6 (Mg_2.6Nd_0.4Zn_0.4Zr) alloy were designed, and the microstructure and precipitation strengthening mechanisms were discussed. After the pre-aging treatment, a large amount of G.P. [...] Read more.

In the present study, different solid solution and aging processes of as-cast and as-compressed ZM6 (Mg_2.6Nd_0.4Zn_0.4Zr) alloy were designed, and the microstructure and precipitation strengthening mechanisms were discussed. After the pre-aging treatment, a large amount of G.P. zones formed in the α-Mg matrix over the course of the subsequent secondary G.P. prescription, where the fine and dispersed Mg₁₂(Nd,Zn) phases were precipitated at the grain boundaries. The pre-aging and secondary aging processes resulted in the Mg₁₂(Nd,Zn) phase becoming globular, preventing grain boundary sliding and decreasing grain boundary diffusion. Meanwhile, precipitation phase â″(Mg₃Nd) demonstrated a coherent relationship with the α-Mg matrix after the pre-aging process, and after the secondary aging phase, Mg₁₂Nd increases and became semi-coherent in the matrix. Compared to an as-cast ZM6 alloy, the yield strength of the as-compressed ZM6 alloy increased sharply due to an increase in the yield strength that was proportional to the particle spacing, where the dislocation bypassed the second phase particle. Compared to the single-stage aging process, the two-stage aging process greatly improved the mechanical properties of both the as-cast and as-compressed ZM6 alloys. The difference between the as-cast and as-compressed states is that an as-compressed ZM6 alloy with more dislocations and twins has more dispersed precipitates in the G.P. zones after secondary aging, meaning that it is greatly strengthened after the two-stage aging treatment process. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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21 pages, 11817 KiB

Open AccessArticle

Characteristic Features of Ultrafine-Grained Ti-45 wt.% Nb Alloy under High Cycle Fatigue

by Aikol M. Mairambekova, Anna Y. Eroshenko, Vladimir A. Oborin, Mikhail V. Bannikov, Valentina V. Chebodaeva, Alena I. Terekhina, Oleg B. Naimark, Andrey I. Dmitriev and Yurii P. Sharkeev

Materials 2021, 14(18), 5365; https://doi.org/10.3390/ma14185365 - 17 Sep 2021

Cited by 4 | Viewed by 2123

Abstract

The paper presents the results of fatigue-testing ultrafine-grained and coarse-grained Ti-45 wt.% Nb alloy samples under very high cycle fatigue (gigacycle regime), with the stress ratio R = −1. The ultrafine-grained (UFG) structure in the investigated alloy was formed by the two-stage SPD [...] Read more.

The paper presents the results of fatigue-testing ultrafine-grained and coarse-grained Ti-45 wt.% Nb alloy samples under very high cycle fatigue (gigacycle regime), with the stress ratio R = −1. The ultrafine-grained (UFG) structure in the investigated alloy was formed by the two-stage SPD method, which included multidirectional forging (abc–forging) and multipass rolling in grooved rollers, with further recrystallization annealing. The UFG structure of the Ti-45 wt.% Nb alloy samples increased the fatigue limit under the high-cycle fatigue conditions up to 1.5 times compared with that of the coarse-grained (CG) samples. The infrared thermography method was applied to investigate the evolution of temperature fields in the samples under cyclic loading. Based on numerical morphology analysis, the scale invariance (the Hurst exponent) and qualitative differences for UFG and CG structures were determined. The latter resulted from the initiation and propagation of fatigue cracks in both ultra-fine grained and coarse-grained alloy samples under very high-cycle fatigue loading. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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11 pages, 4139 KiB

Open AccessArticle

Effect of Direct Powder Forging Process on the Mechanical Properties and Microstructural of Ti-6Al-4V ELI

by Sébastien Germain Careau, Bernard Tougas and Elena Ulate-Kolitsky

Materials 2021, 14(16), 4499; https://doi.org/10.3390/ma14164499 - 11 Aug 2021

Cited by 6 | Viewed by 2622

Abstract

The study of powder metallurgy processing methods for titanium represents a promising avenue that can respond to a growing demand. This work reports the feasibility of direct powder forging (DPF) as a method to process large spherical Ti-6Al-4V powder into wrought products with [...] Read more.

The study of powder metallurgy processing methods for titanium represents a promising avenue that can respond to a growing demand. This work reports the feasibility of direct powder forging (DPF) as a method to process large spherical Ti-6Al-4V powder into wrought products with noteworthy properties and physical characteristics. Direct powder forging is a thermomechanical process that imparts uniaxial loading to an enclosed and uncompacted powder to produce parts of various sizes and shapes. Stainless steel canisters were filled with prealloyed Ti-6Al-4V powder and consolidated through a multi-step open-die forging and rolling process into wrought DPF bars. After DPF, annealing was performed in the upper α+β phase. The results show that full consolidation was achieved and higher mechanical properties than the Ti-6Al-4V grade F-23 requirements in annealed conditions were obtained. The results also show that direct powder forging of spherical titanium powder could produce wrought mill products and exhibit some potential for further investigation for industrial applications. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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14 pages, 8031 KiB

Open AccessArticle

The Application of Convolutional Neural Networks (CNNs) to Recognize Defects in 3D-Printed Parts

by Hao Wen, Chang Huang and Shengmin Guo

Materials 2021, 14(10), 2575; https://doi.org/10.3390/ma14102575 - 15 May 2021

Cited by 15 | Viewed by 4149

Abstract

Cracks and pores are two common defects in metallic additive manufacturing (AM) parts. In this paper, deep learning-based image analysis is performed for defect (cracks and pores) classification/detection based on SEM images of metallic AM parts. Three different levels of complexities, namely, defect [...] Read more.

Cracks and pores are two common defects in metallic additive manufacturing (AM) parts. In this paper, deep learning-based image analysis is performed for defect (cracks and pores) classification/detection based on SEM images of metallic AM parts. Three different levels of complexities, namely, defect classification, defect detection and defect image segmentation, are successfully achieved using a simple CNN model, the YOLOv4 model and the Detectron2 object detection library, respectively. The tuned CNN model can classify any single defect as either a crack or pore at almost 100% accuracy. The other two models can identify more than 90% of the cracks and pores in the testing images. In addition to the application of static image analysis, defect detection is also successfully applied on a video which mimics the AM process control images. The trained Detectron2 model can identify almost all the pores and cracks that exist in the original video. This study lays a foundation for future in situ process monitoring of the 3D printing process. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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9 pages, 5149 KiB

Open AccessArticle

Comparison on Tensile Characteristics of Plain C–Mn Steel with Ultrafine Grained Ferrite/Cementite Microstructure and Coarse Grained Ferrite/Pearlite Microstructure

by Yan Tian, Mingchun Zhao, Wenjian Liu, Jimou Zhang, Min Zhang, Hongying Li, Dengfeng Yin and Andrej Atrens

Materials 2021, 14(9), 2309; https://doi.org/10.3390/ma14092309 - 29 Apr 2021

Cited by 7 | Viewed by 2308

Abstract

This work investigated the tensile characteristics of plain C–Mn steel with an ultrafine grained ferrite/cementite (UGF/C) microstructure and coarse-grained ferrite/pearlite (CGF/P) microstructure. The tensile tests were performed at temperatures between 77 K and 323 K. The lower yield and the ultimate tensile strengths [...] Read more.

This work investigated the tensile characteristics of plain C–Mn steel with an ultrafine grained ferrite/cementite (UGF/C) microstructure and coarse-grained ferrite/pearlite (CGF/P) microstructure. The tensile tests were performed at temperatures between 77 K and 323 K. The lower yield and the ultimate tensile strengths were significantly increased when the microstructure was changed from the CGF/P to the UGF/C microstructures, but the total elongation and the uniform elongation decreased. A microstructural change from the CGF/P microstructure to the UGF/C microstructure had an influence on the athermal component of the lower yield and the ultimate tensile strengths but not on the thermal component. The UGF/C microstructure with a higher carbon content provided a higher strength without losing ductility because cementite particles restrained necking. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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17 pages, 5778 KiB

Open AccessArticle

Sacrificial Dissolution of Zinc Electroplated and Cold Galvanized Coated Steel in Saline and Soil Environments: A Comparison

by Ameeq Farooq, Umer Masood Chaudry, Ahsan Saleem, Kashif Mairaj Deen, Kotiba Hamad and Rafiq Ahmad

Materials 2021, 14(4), 744; https://doi.org/10.3390/ma14040744 - 5 Feb 2021

Cited by 6 | Viewed by 2378

Abstract

To protect steel structures, zinc coatings are mostly used as a sacrificial barrier. This research aims to estimate the dissolution tendency of the electroplated and zinc-rich cold galvanized (ZRCG) coatings of a controlled thickness (35 ± 1 μm) applied via brush and dip [...] Read more.

To protect steel structures, zinc coatings are mostly used as a sacrificial barrier. This research aims to estimate the dissolution tendency of the electroplated and zinc-rich cold galvanized (ZRCG) coatings of a controlled thickness (35 ± 1 μm) applied via brush and dip coating methods on the mild steel. To assess the corrosion behavior of these coated samples in 3.5% NaCl and 10% NaCl containing soil solutions, open circuit potential (OCP), cyclic polarization (CP), and electrochemical impedance spectroscopy (EIS) tests were performed. The more negative OCP and appreciably large corrosion rate of the electroplated and ZRCG coated samples in 3.5% NaCl solution highlighted the preferential dissolution of Zn coatings. However, in saline soil solution, the relatively positive OCP (>−850 mV vs. Cu/CuSO₄) and lower corrosion rate of the electroplated and ZRCG coatings compared to the uncoated steel sample indicated their incapacity to protect the steel substrate. The CP scans of the zinc electroplated samples showed a positive hysteresis loop after 24 h of exposure in 3.5% NaCl and saline soil solutions attributing to the localized dissolution of the coating. Similarly, the appreciable decrease in the charge transfer resistance of the electroplated samples after 24 h of exposure corresponded to their accelerated dissolution. Compared to the localized dissolution of the electroplated and brush-coated samples, the dip-coated ZRCG samples exhibited uniform dissolution during the extended exposure (500 h) salt spray test. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Steels)

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