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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (20 January 2024) | Viewed by 23213

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Dr. Xiaoqing Si

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State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China
Interests: welding and joining; microstructure characterization; titanium alloys; nanomaterials; properties; interface engineering; coating
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Dear Colleagues,

It is my pleasure to invite you to submit a manuscript to the Special Issue “Microstructure and Mechanical Properties of Alloys” in Materials (Impact Factor: 3.748).

Metal alloys are widely used in industrial products, and their microstructure and mechanical properties directly affect the performance of products. During the whole life cycle of a metal product, its microstructure and mechanical properties will undergo multiple stages of evolution. Firstly, the preparation of alloys, including metallurgy, casting and rolling, determines the initial properties of alloys. Afterward, alloys will undergo welding, joining or machining processes in order to manufacture metal products, which will also affect the microstructure and mechanical properties of alloys. Finally, during the service process of metal products, they will experience high-temperature, -oxidation or -corrosion environments, which will affect the microstructure and mechanical properties of alloys to varying degrees. It is crucial to study the micro store and properties of alloys in the whole life cycle to promote the development and application of alloys.

The aim of this Special Issue is to provide an updated outlook on the microstructure and mechanical properties of alloys at various stages, including the preparation, processing and service stages. Especially the correspondence between alloys microstructure and mechanical properties needs to be established. These papers can help resolve and understand the evolution of properties of alloys products at different stages. This will help to adjust and design the microstructure and mechanical properties of alloys throughout the whole life cycle.

This Special Issue represents a good opportunity for researchers around the world to disseminate different aspects of their work and report the results related to this topic.

Research articles, review articles, and communications are invited for submission to this Special Issue.

Dr. Xiaoqing Si
Guest Editor

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Keywords

microstructure characterization
mechanical properties
metals and alloys
welding and joining
improvement of properties
machining methods
joint strength
microstructure evolution
corrosion resistance

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Published Papers (12 papers)

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Research

15 pages, 5456 KiB

Open AccessArticle

Influence of an Engineered Notch on the Electromagnetic Radiation Performance of NiTi Shape Memory Alloy

by Anu Anand, Rajeev Kumar, Shatrudhan Pandey, S. M. Mozammil Hasnain and Saurav Goel

Materials 2024, 17(7), 1708; https://doi.org/10.3390/ma17071708 - 8 Apr 2024

Viewed by 1457

Abstract

This work explores the influence of a pre-engineered notch on the electromagnetic radiation (EMR) parameters in NiTi shape memory alloy (SMA) during tensile tests. The test data showed that the EMR signal fluctuated between oscillatory and exponential, signifying that the specimen’s viscosity damping coefficient changes during strain hardening. The EMR parameters, maximum EMR amplitude, and average EMR energy release rate remained constant initially but rose sharply with the plastic zone radius with progressive loading. It was postulated that new Frank–Read sources permit dislocation multiplication and increase the number of edge dislocations participating in EMR emissions, leading to a rise in the value of EMR parameters. The study of the correlation between EMR emission parameters and the plastic zone radius before the crack tip is a vital crack growth monitoring tool. An analysis of the interrelationship of the EMR energy release rate at fracture with the elastic strain energy release rate would help develop an innovative approach to assess fracture toughness, a critical parameter for the design and safety of metals. The microstructural analysis of tensile fractures and the interrelation between deformation behaviours concerning the EMR parameters offers a novel and real-time approach to improve the extant understanding of the behaviour of metallic materials. Full article

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

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12 pages, 6951 KiB

Open AccessArticle

Study on the Effect of “3D-rGO” Buffer Layer on the Microstructure and Properties of SiO_2f/SiO₂ and TC4 Brazed Joint

by Peng Liu, Qiang Ma, Yongwei Chen, Shujin Chen, Jie Zhu, Peng He, Xiaojiang Chen, Xiao Jin and Bin Zheng

Materials 2024, 17(6), 1394; https://doi.org/10.3390/ma17061394 - 19 Mar 2024

Viewed by 1271

Abstract

Brazing a SiO_2f/SiO₂ composite with metals is often faced with two problems: poor wettability with the brazing alloy and high residual stress in the joint. To overcome these problems, we report a combined method of selective etching and depositing reduced graphene oxide (rGO) on the surface of a SiO_2f/SiO₂ composite (3D-rGO-SiO_2f/SiO₂) to assist brazing with TC4. After the combined treatment, a “3D-rGO” buffer layer formed on the surface layer of the SiO_2f/SiO₂, and the contact angle was reduced from 130° to 38°, which meant the wettability of active brazing alloy on the surface of SiO_2f/SiO₂ was obviously improved. In addition, the “3D-rGO” buffer layer contributed to fully integrating the brazing alloy and SiO_2f/SiO₂; then, the infiltration of the brazing alloy into the surface layer of the SiO_2f/SiO₂ was enhanced and formed the reduced graphene oxide with a pinning structure in the three dimensional (“3D-pinning-rGO”) structure. Moreover, the joining area of the brazing alloy and SiO_2f/SiO₂ was expanded and the mismatch degree between the SiO_2f/SiO₂ and TC4 was reduced, which was achieved by the “3D-pinning-rGO” structure. Furthermore, the concentration of the residual stress in the SiO_2f/SiO₂-TC4 joints transferred from the SiO_2f/SiO₂ to the braided quartz fibers, and the residual stress reduced from 142 MPa to 85 MPa. Furthermore, the 3D-pinning-rGO layer facilitated the transfer of heat between the substrates during the brazing process. Finally, the shear strength of the SiO_2f/SiO₂-TC4 joints increased from 12.5 MPa to 43.7 MPa by the selective etching and depositing rGO method. Full article

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

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14 pages, 4992 KiB

Open AccessArticle

3D Model of Carbon Diffusion during Diffusional Phase Transformations

by Łukasz Łach and Dmytro Svyetlichnyy

Materials 2024, 17(3), 674; https://doi.org/10.3390/ma17030674 - 30 Jan 2024

Cited by 1 | Viewed by 1299

Abstract

The microstructure plays a crucial role in determining the properties of metallic materials, in terms of both their strength and functionality in various conditions. In the context of the formation of microstructure, phase transformations that occur in materials are highly significant. These are processes during which the structure of a material undergoes changes, most commonly as a result of variations in temperature, pressure, or chemical composition. The study of phase transformations is a broad and rapidly evolving research area that encompasses both experimental investigations and modeling studies. A foundational understanding of carbon diffusion and phase transformations in materials science is essential for comprehending the behavior of materials under different conditions. This understanding forms the basis for the development and optimization of materials with desired properties. The aim of this paper is to create a three-dimensional model for carbon diffusion in the context of modeling diffusional phase transformations occurring in carbon steels. The proposed model relies on the utilization of the LBM (Lattice Boltzmann Method) and CUDA architecture. The resultant carbon diffusion model is intricately linked with a microstructure evolution model grounded in FCA (Frontal Cellular Automata). This manuscript provides a concise overview of the LBM and the FCA method. It outlines the structure of the developed three-dimensional model for carbon diffusion, details its correlation with the microstructure evolution model, and presents the developed algorithm for simulating carbon diffusion. Demonstrative examples of simulation results, illustrating the growth of the emerging phase and affected by various model parameters within particular planes of the 3D calculation domain, are also presented. Full article

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

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16 pages, 4271 KiB

Open AccessArticle

Recycling of Hard Disk Drive Platters via Plastic Consolidation

by Tomasz Skrzekut, Maciej Wędrychowicz and Andrzej Piotrowicz

Materials 2023, 16(20), 6745; https://doi.org/10.3390/ma16206745 - 18 Oct 2023

Viewed by 3165

Abstract

The paper presents the comparison of two methods of recycling aluminum from HDD platters—the melting method and the method of plastic consolidation. The main elements of HDD memory, i.e., data carriers (platters), were examined via the percentage share of the total HDD mass and also via EDS analysis. The most common are platters made of the aluminum alloy series 5XXX, which are covered with a thin magnetic layer made of nickel. The research involved removing data carriers from about 30 HDDs and fragmenting them. The next step was to divide the platters into three groups; one was melted, the second was subjected to plastic consolidation, and the third group was fragmented into chips and also subjected to the consolidation process. Then, in the process of co-extrusion, rods were extruded from each material, and were subjected to EDS analysis, microstructure testing, Vickers hardness, and uniaxial tensile tests, and then the obtained results were compared. The obtained results of the microstructural tests in the case of gravity cast material confirmed the presence of the Al3Ni globular phase in the matrix. In the case of pressed and extruded materials, the Al3Ni phase appeared at the Ni-AlMg contact. After plastic consolidation, all the tested rods were characterized by their comparable strength properties (a tensile strength of 250 MPa and yield strength of 105 MPa). Full article

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

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12 pages, 6992 KiB

Open AccessArticle

Effect of Cold Rolling Reduction Rate on the Microstructure and Properties of Q&P Steel with a Ferrite-Pearlite Initial Structure

by Shengwei Wang, Mengxiao Chen, Mingyue Yang, Yuhe Huang, Shuize Wang and Xinping Mao

Materials 2023, 16(18), 6102; https://doi.org/10.3390/ma16186102 - 7 Sep 2023

Cited by 2 | Viewed by 1755

Abstract

Quenching and partitioning (Q&P) steel has garnered attention as a promising third-generation automotive steel. While the conventional production (CP) method for Q&P steel involves a significant cumulative cold rolling reduction rate (CRRR) of 60–70%, the thin slab casting and rolling (TSCR) process has emerged as a potential alternative to reduce or eliminate the need for cold rolling, characterized with a streamline production chain, high-energy efficiency, mitigated CO₂ emission and economical cost. However, the effect of the CRRR on the microstructure and properties of Q&P steel with an initial ferrite-pearlite microstructure has been overlooked, preventing the extensive application of TSCR in producing Q&P steel. In this work, investigations involving different degrees of CRRRs reveal a direct relationship between increased reduction and decreased yield strength and plasticity. Notably, changes in the microstructure were observed, including reduced size and proportion of martensite blocks, increased ferrite proportion and decreased retained austenite content. The decrease in yield strength was primarily attributed to the increased proportion of the softer ferrite phase, while the reduction in plasticity was primarily linked to the decrease in retained austenite content. This study provides valuable insights for optimizing the TSCR process of Q&P steel, facilitating its wider adoption in the automotive sector. Full article

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

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17 pages, 5546 KiB

Open AccessArticle

Effect of Cold Drawing and Annealing in Thermomechanical Treatment Route on the Microstructure and Functional Properties of Superelastic Ti-Zr-Nb Alloy

by Anastasia Kudryashova, Konstantin Lukashevich, Mikhail Derkach, Oleg Strakhov, Sergey Dubinskiy, Vladimir Andreev, Sergey Prokoshkin and Vadim Sheremetyev

Materials 2023, 16(14), 5017; https://doi.org/10.3390/ma16145017 - 15 Jul 2023

Cited by 3 | Viewed by 1714

Abstract

In this study, a superelastic Ti-18Zr-15Nb (at. %) alloy was subjected to thermomechanical treatment, including cold rotary forging, intermediate annealing, cold drawing, post-deformation annealing, and additional low-temperature aging. As a result of intermediate annealing, two structures of β-phase were obtained: a fine-grained structure (d ≈ 3 µm) and a coarse-grained structure (d ≈ 11 µm). Cold drawing promotes grain elongation in the drawing direction; in a fine-grained state, grains form with a size of 4 × 2 µm, and in a coarse-grained state, they grow with a size of 16 × 6 µm. Post-deformation annealing (PDA) at 550 °C for 30 min leads to grain sizes of 5 µm and 3 µm, respectively. After PDA at 550 °C (30 min) in the fine-grained state, the wire exhibits high tensile strength (UTS = 624 MPa), highest elongation to failure (δ ≥ 8%), and maximum difference between the dislocation and transformation yield stresses, as well as the highest superelastic recovery strain (ε_r^SE ≥ 3.3%) and total elastic + superelastic recovery strain (ε_r^el+SE ≥ 5.4%). Additional low-temperature aging at 300 °C for 30–180 min leads to ω-phase formation, alloy hardening, embrittlement, and a significant decrease in superelastic recovery strain. Full article

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

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12 pages, 6662 KiB

Open AccessArticle

Integrated Computing Accelerates Design and Performance Control of New Maraging Steels

by Shixing Chen, Jingchuan Zhu, Tingyao Liu, Yong Liu, Yudong Fu, Toshihiro Shimada and Guanqi Liu

Materials 2023, 16(12), 4273; https://doi.org/10.3390/ma16124273 - 8 Jun 2023

Viewed by 1831

Abstract

This paper mainly used database technology, machine learning, thermodynamic calculation, experimental verification, etc., on integrated computational materials engineering. The interaction between different alloying elements and the strengthening effect of precipitated phases were investigated mainly for martensitic ageing steels. Modelling and parameter optimization were performed by machine learning, and the highest prediction accuracy was 98.58%. We investigated the influence of composition fluctuation on performance and correlation tests to analyze the influence of elements from multiple perspectives. Furthermore, we screened out the three-component composition process parameters with composition and performance with high contrast. Thermodynamic calculations studied the effect of alloying element content on the nano-precipitation phase, Laves phase, and austenite in the material. The heat treatment process parameters of the new steel grade were also developed based on the phase diagram. A new type of martensitic ageing steel was prepared by selected vacuum arc melting. The sample with the highest overall mechanical properties had a yield strength of 1887 MPa, a tensile strength of 1907 MPa, and a hardness of 58 HRC. The sample with the highest plasticity had an elongation of 7.8%. The machine learning process for the accelerated design of new ultra-high tensile steels was found to be generalizable and reliable. Full article

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

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21 pages, 12143 KiB

Open AccessArticle

Effects of Cu Addition on Age Hardening Behavior and Mechanical Properties of High-Strength Al-1.2Mg-1.2Si Alloy

by Xu Zhang, Lizhen Yan, Zhihui Li, Xiwu Li, Guanjun Gao, Hongwei Yan, Kai Wen, Yongan Zhang and Baiqing Xiong

Materials 2023, 16(8), 3126; https://doi.org/10.3390/ma16083126 - 15 Apr 2023

Cited by 7 | Viewed by 1850

Abstract

In this study, the effects of Cu addition on artificial age hardening behavior and mechanical properties of Al-1.2Mg-1.2Si-(xCu) alloy was investigated quantitatively and qualitatively by Vickers hardness, tensile test, and transmission electron microscope. The results indicated that Cu addition enhanced the aging response of the alloy at 175 °C. With the increase in Cu content, the time for the alloys to reach peak aging decreased from 12 h to 10 h and 8 h. The tensile strength of the alloy was obviously improved with Cu added in which was 421 MPa of 0Cu alloy, 448 MPa of 0.18Cu alloy, and 459 MPa of 0.37Cu alloy. The results of TEM observation revealed that the addition of 0.37Cu changed the aging precipitation sequence of the alloy, in which the precipitation sequence of 0Cu and 0.18Cu alloy was SSSS→GP zones/pre-β″→β″→β″ + β′, 0.37Cu alloy was SSSS→GP zones/pre-β″→β″ + L→β″ + L + Q′. Moreover, with the addition of Cu, the number density and volume fraction of precipitates of the Al-1.2Mg-1.2Si-(xCu) alloy was evidently increased. The number density was increased from 0.23 × 10²³/m³ to 0.73 × 10²³/m³ in the initial aging stage and from 1.9 × 10²³/m³ to 5.5 × 10²³/m³ in the peak aging stage. The volume fraction was increased from 0.27% to 0.59% in the early aging stage and from 4.05% to 5.36% in the peak aging stage. It indicated that Cu addition promoted the precipitation of strengthening precipitates and boosted the mechanical properties of the alloy accordingly. Full article

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

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10 pages, 6052 KiB

Open AccessArticle

The Effect of Hydrogen on Plastic Anisotropy of Mg and α-Ti/Zr from First-Principles Calculations

by Jiwei Wang, Bin Shao, Debin Shan, Bin Guo and Yingying Zong

Materials 2023, 16(8), 3016; https://doi.org/10.3390/ma16083016 - 11 Apr 2023

Viewed by 1530

Abstract

Mg and α-Ti/Zr exhibit high plastic anisotropy. In this study, the ideal shear strength across the basal, prismatic, pyramidal I, and pyramidal II slip systems in Mg and α-Ti/Zr with and without hydrogen was computed. The findings indicate that hydrogen reduces the ideal shear strength of Mg across the basal and pyramidal II slip systems, as well as of α-Ti/Zr across all four systems. Moreover, the activation anisotropy of these slip systems was analyzed based on the dimensionless ideal shear strength. The results suggest that hydrogen increases the activation anisotropy of these slip systems in Mg, while decreasing it in α-Ti/Zr. Furthermore, the activation possibility of these slip systems in polycrystalline Mg and α-Ti/Zr subjected to uniaxial tension was analyzed by utilizing the ideal shear strength and Schmidt’s law. The results reveal that hydrogen increases the plastic anisotropy of Mg/α-Zr alloy while decreasing that of α-Ti alloy. Full article

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

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17 pages, 6528 KiB

Open AccessArticle

Constitutive Analysis and Microstructure Characteristics of As-Homogenized 2198 Al–Li Alloy under Different Hot Compression Deformation Conditions

by Huiyu Li, Xiwu Li, Hongwei Yan, Yanan Li, Libo Geng, Chenyang Xun, Zhihui Li, Yongan Zhang and Baiqing Xiong

Materials 2023, 16(7), 2660; https://doi.org/10.3390/ma16072660 - 27 Mar 2023

Cited by 4 | Viewed by 1637

Abstract

The 2198 Al–Li alloy has unique superiority in mechanical performance and has been extensively used in the aerospace field. In this study, the hot deformation behavior of the 2198 Al–Li alloy was investigated on a Gleeble-1500 thermomechanical simulator with a strain rate of 0.01–10 s⁻¹ in the temperature range of 330–510 °C. The Arrhenius constitutive equation of the alloy was established based on the true stress–strain curves to describe the rheology behaviors during the deformation of the alloy. The processing maps under the strain of 0.2–0.8 were constructed, which indicates the efficiency of power dissipation and instability of the deformed alloy. It was found that the instability domains are more likely to occur in the regions of low deformation temperature and high strain rate, corresponding to the high Zener–Hollomon (Z) parameter. The microstructure evolution of the studied alloy with different Z parameters was characterized. Then, the dynamic recrystallization (DRX) behavior was studied by electron backscatter diffraction, and the misorientation angle of deformed specimens was analyzed. The effect of different deformation temperatures and strain rates on the microstructure of the alloy and the behavior of dislocations and precipitations were investigated by transmission electron microscopy. The results demonstrate that continuous dynamic recrystallization (CDRX) and geomatic dynamic recrystallization (GDRX) mainly occur at the deformation conditions of a low Z value, and discontinuous dynamic recrystallization (DDRX) is likely to occur with increasing Z values. Full article

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

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14 pages, 7873 KiB

Open AccessArticle

Effect of Intercritical Temperature on the Microstructure and Mechanical Properties of a Ferritic–Martensitic Dual-Phase Low-Alloy Steel with Varying Nickel Content

by Esteban Rodoni, Kim Verbeken, Tom Depover and Mariano Iannuzzi

Materials 2022, 15(24), 9018; https://doi.org/10.3390/ma15249018 - 16 Dec 2022

Cited by 2 | Viewed by 2148

Abstract

Dual-phase low-alloy steels combine a soft ferrite phase with a hard martensite phase to create desirable properties in terms of strength and ductility. Nickel additions to dual-phase low-alloy steels can increase the yield strength further and lower the transformation temperatures, allowing for microstructure refining. Determining the correct intercritical annealing temperature as a function of nickel content is paramount, as it defines the microstructure ratio between ferrite and martensite. Likewise, quantifying the influence of nickel on the intercritical temperature and its synergistic effect with the microstructure ratio on mechanical properties is vital to designing dual-phase steels suitable for corrosive oil and gas services as well as hydrogen transport and storage applications. In this work, we used a microstructural design to develop intercritical annealing heat treatments to obtain dual-phase ferritic–martensitic low-alloy steels. The intercritical annealing and tempering temperatures and times were targeted to achieve three different martensite volume fractions as a function of nickel content, with a nominal content varying between 0, 1, and 3-wt% Ni. Mechanical properties were characterized using tensile testing and microhardness measurements. Additionally, the microstructure was studied using scanning electron microscopy coupled with electron backscatter diffraction analysis. Tensile strength increased with increasing martensite ratio and nickel content, with a further grain refinement effect found in the 3-wt% Ni steel. The optimal heat treatment parameters for oil and gas and hydrogen transport applications are discussed. Full article

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

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15 pages, 9788 KiB

Open AccessArticle

Carbides Dissolution in 5Cr15MoV Martensitic Stainless Steel and New Insights into Its Effect on Microstructure and Hardness

by Wenle Liu, Xuelin Wang, Fujian Guo and Chengjia Shang

Materials 2022, 15(24), 8742; https://doi.org/10.3390/ma15248742 - 7 Dec 2022

Cited by 13 | Viewed by 2228

Abstract

The dissolution behavior of carbides in martensitic stainless steel and its effect on microstructure and hardness were investigated by using X-ray diffractometer (XRD) and field emission scanning electron microscopy (FE-SEM) with energy dispersive spectrometer (EDS) and electron backscattering diffraction (EBSD). The results indicated that the microstructure after austenitizing heat treatment and oil quenched consisted of martensite, M₂₃C₆ carbides and retained austenite. The temperature and particle size had great influence on the dissolution of carbides. The EBSD results showed that the twin-related variant pair V1/V2 governed the phase transformation. Meanwhile, the density of high-angle grain boundaries (HAGBs) increased with the increase of austenitizing temperature from 950 to 1150 °C. The hardness test results indicated that the hardness first increased and then decreased with the increase of the austenitizing temperature, and the peak appeared at 1050 °C with a Rockwell hardness value of 59.8 HRC. A model was established to quantitatively explain the contribution of different microstructures to hardness. The contribution to hardness came mainly from martensite. The retained austenite had a negative effect on hardness when the volume fraction was more than 10%. In contrast, carbides contributed less to hardness due to their small content. Full article

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

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