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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (31 January 2026) | Viewed by 13321

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Dr. Guodong Cui

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Faculty of Metal Materials Department, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China
Interests: metal heat treatment; surface modification; powder modification; sintering; phase transformation; green manufacturing and remanufacturing
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Dr. Chengsong Zhang

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Faculty of Metal Materials Department, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China
Interests: metal heat treatment; surface modification; computational materials science
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Heat treatment is the foundation of modern manufacturing; it improves the properties of metal materials by changing their microstructure. Almost all important mechanical components require heat treatment to improve their performance and enhance their service safety. Advancements in heat treatment equipment and technology have greatly promoted the development of advanced metal materials, laying the foundation for the upgrading and development of future manufacturing industries. The scope of this Special Issue includes the following: progress in heat treatment, the relationship between heat treatment processes, microstructures and their properties, the heat treatment of new materials, the application of heat treatment in advanced metal preparation, and the relationship between heat treatment and the environment. Heat treatment is the soul of mechanical components, providing infinite possibilities for improving and optimizing the performance of metal materials. We aim to provide a platform where researchers can learn about the research and development of heat treatment and create space for the performance and quality improvement of advanced equipment in the future.

In this Special Issue, we welcome articles that focus on discussing the relationship between advanced heat treatment processes, microstructures, and their properties. Technology enabling green, intelligent, and low-cost heat treatment processes is particularly interesting and has the potential for implementation in advanced metal manufacturing and performance improvement. We look forward to receiving your contributions.

Dr. Guodong Cui
Dr. Chengsong Zhang
Guest Editors

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Keywords

heat treatment
microstructure
mechanical properties
characterization
mechanical components
green manufacturing

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Published Papers (11 papers)

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Research

13 pages, 35378 KB

Open AccessArticle

Austenite Formation and Decomposition in a High-Strength Alloy Subjected to Heating and Cooling Cycles

by Laura Fátima Zúñiga Pineda, Omar García Rincón and Martha Patricia Guerrero Mata

Metals 2026, 16(3), 297; https://doi.org/10.3390/met16030297 - 7 Mar 2026

Viewed by 289

Abstract

This study investigates the critical transformation temperatures of a high-strength API-grade steel through thermal analysis and software simulations; the precise determination of these temperatures is essential for enhancing the efficacy of subsequent experimental trials. Utilizing the ‘Quench Properties’ module of JMatPro^® V14, characteristic transformations were identified between 950 °C and 25 °C under stable conditions. Heating rates of 5, 10, and 30 °C/s were applied to determine critical temperatures, with Ac₁ ranging from 700 °C to 750 °C and Ac₃ from 850 °C to 900 °C. Niobium content may influence Ac₁ and Ac₃, promoting the ferritic phase and elevating transformation temperatures at a heating rate of 30 °C/s. Conversely, a rate of 10 °C/s significantly influenced austenite formation, impacting the development of microconstituents that enhance both strength and elongation post-quenching. Furthermore, slow cooling was found to favor the premature formation of allotriomorphic ferrite, which hinders the transformation of austenite into bainite and martensite during accelerated cooling. Finally, this study corroborates that JMatPro^® is a reliable tool for predicting critical temperatures and designing optimized thermomechanical processing routes. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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29 pages, 23362 KB

Open AccessArticle

Effects of Solution Treatment and Artificial Aging on the Microstructure and Mechanical Properties of TiB₂/7050 Composites

by Zhiwei Wu, Wenfeng Han and Binxian Yuan

Metals 2026, 16(3), 294; https://doi.org/10.3390/met16030294 - 5 Mar 2026

Viewed by 330

Abstract

This study investigates the solution and artificial aging processes of TiB₂/7050 composites. Using microscopic and mechanical tests, we systematically evaluate the material’s microstructural evolution and mechanical performance, aiming to optimize heat treatment parameters. The study shows that a solution temperature of 475 °C for 1 h is optimal for fully dissolving the second-phase particles. Regarding artificial aging, peak hardness of 246 HV is achieved at 140 °C for 16 h. Analysis of the phases and microstructure in O and T6-states shows that strengthening occurs through grain boundary hardening and precipitation hardening. The effect of TiB₂ particles on the above process was also explored. During solidification, TiB₂ particles were pushed by the advancing solid–liquid interface and primarily distributed along grain boundaries. This distribution subsequently slowed the solid solution process by reducing the contact area between the η(MgZn₂) phase and the α(Al) matrix. During aging, they enhance grain boundary precipitates (GBPs) in particle-rich regions and inhibit the formation of precipitate-free zones (PFZs), with a concentration of the η’ phase forming around the particles. Beyond a certain distance from the particles, there is a decrease in η’ phase concentration. This study is expected to contribute to advanced lightweight materials research and development, opening up new opportunities for their application in various industries. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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22 pages, 4323 KB

Open AccessArticle

Effect of Tempering on Microstructure, Strength and Toughness Gradient in Quenched Low-Alloy Medium-Thickness Steel Plate

by Boyu Guan, Shaobin Bai, Yongqing Zhang, Peimao Fu, Haitao Lu, Hejia Zhu, Xingchi Chen, Kaikai Guo, Haonan Wang and Yongan Chen

Metals 2026, 16(3), 243; https://doi.org/10.3390/met16030243 - 24 Feb 2026

Viewed by 353

Abstract

To elucidate how tempering temperature influences through-thickness microstructure and strength–toughness gradients in an online direct-quenched (DQ) low-alloy medium-thick plate, a 25-mm plate was direct-quenched from 900 °C to <150 °C and tempered at 530 °C × 1.5 h or 580 °C × 1.5 h. Tensile and room-temperature Charpy V-notch impact testing and microstructure characterization were performed at the upper surface, mid-thickness, and lower surface. In the as-DQ state, the upper surface contained ferrite (F, ~60%) and granular bainite (GB, ~30%) with minor lath bainite (LB, ~10%) and a small amount of martensite/austenite (M/A). The mid-thickness and lower surface remained dominated by F + GB (mid-thickness: GB~50%, F~30%, M/A~20%; lower surface: F~85%, GB~15%); the mid-thickness showed the lowest yield strength/ultimate tensile strength (YS/UTS) of 498/675 MPa. In the as-DQ state, the room-temperature Charpy V-notch absorbed energies at the upper surface, mid-thickness, and lower surface were 223.23, 229.88, and 261.22 J, respectively, indicating a pronounced through-thickness variation (ΔE_(max–min) ≈ 38 J). After tempering at 530 °C, the upper surface and mid-thickness developed an F + tempered sorbite (TS) microstructure (upper surface: F~70%, TS~30%; mid-thickness: F~60%, TS~40%), whereas the lower surface was mainly ferrite with a small amount of spheroidized carbides/tempered cementite (SC). The mid-thickness YS/UTS increased to 619/805 MPa, and the impact energies at the upper surface and mid-thickness increased to 240.62 J and 235.56 J, respectively, resulting in a reduced through-thickness gradient. After 580 °C tempering, recovery and polygonal ferrite formation dominated; surface yield strength increased but mid-thickness yield improvement was limited. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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22 pages, 4238 KB

Open AccessArticle

Tailored Annealing for Interfacial Design and Mechanical Optimization of Cu18150/Al1060/Cu18150 Trilayer Composites

by Yuchao Zhao, Mahmoud Ebrahimi, Linfeng Wu, Shokouh Attarilar and Qudong Wang

Metals 2026, 16(2), 176; https://doi.org/10.3390/met16020176 - 1 Feb 2026

Viewed by 415

Abstract

Copper–aluminum layered composites offer a promising combination of high conductivity, light weight, and cost-effectiveness, making them attractive for applications in electric vehicles, electronics, and power transmission. However, achieving reliable interfacial bonding while avoiding excessive work hardening and brittle intermetallic formation remains a significant challenge. In this study, a Cu18150/Al1060/Cu18150 trilayer composite was fabricated through a three-stage high-temperature oxygen-free rolling process. Subsequently, the produced composite was subjected to annealing treatments to systematically investigate the effects of rolling passes, annealing temperature/time on interfacial evolution and mechanical behavior. Results indicate that rolling passes primarily influence interfacial topography and defect distribution. Fewer passes lead to wavy, mechanically bonded interfaces, while more passes improve flatness but reduce intermetallic continuity. Annealing temperature critically governs diffusion kinetics; temperatures up to 400 °C promote the formation of a uniform Al₂Cu layer, whereas 450 °C accelerates the growth of brittle Al₄Cu₉, thickening the intermetallic layer to 18 μm and compromising toughness. Annealing duration further modulates diffusion mechanisms, with short-term (0.5 h) treatments favoring defect-assisted diffusion, resulting in a porous, rapidly thickened layer. In contrast, longer annealing (≥1 h) shifts toward lattice diffusion, which densifies the interface but risks excessive brittle phase formation if prolonged. Mechanical performance evolves accordingly; as-rolled strength increases with the number of rolling passes, but at the expense of ductility. Annealing transforms bonding from a mechanical to a metallurgical condition, shifting fracture from delamination to collaborative failure. The identified optimal process, single-pass rolling followed by annealing at 420 °C for 1 h, yields a balanced interfacial structure of Al₂Cu, AlCu, and Al₄Cu₉ phases, achieving a tensile strength of 258.9 MPa and an elongation of 28.2%, thereby satisfying the target performance criteria (≥220 MPa and ≥20%). Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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14 pages, 15800 KB

Open AccessArticle

Effect of Heat Treatment Process on Microstructure and Mechanical Properties of As-Cast Mg-8Gd-1Y-2Sm-1.2Zn-0.5Mn Alloy

by Zirui Qiao, Feng Wang, Chun Xue, Chaojie Che and Zhibing Chu

Metals 2026, 16(2), 145; https://doi.org/10.3390/met16020145 - 25 Jan 2026

Cited by 1 | Viewed by 380

Abstract

This study investigates the as-cast Mg-8Gd-1Y-2Sm-1.2Zn-0.5Mn (wt.%) alloy with high rare-earth content. Solution treatments were conducted at 480 °C, 520 °C, and 560 °C for 6–10 h. Microstructure and mechanical properties were characterized using OM, XRD, SEM-EDS, and compression testing. The as-cast alloy shows a dendritic structure with continuous grain-boundary phases (Mg₅RE, W, and LPSO), exhibiting a compressive yield strength of 145 MPa, ultimate strength of 238 MPa, and fracture strain of 12.66%. Solution temperature has a critical influence on phase dissolution and grain refinement. Notably, the overall plasticity of the material did not show a significant dependence on the specific solution temperature or holding time within the studied range. Treatment at 520 °C produces the most balanced microstructure: clear grain boundaries, extensive phase dissolution, refined grains, and enhanced solid-solution strengthening. Specifically, 520 °C for 10 h results in the finest and most uniformly distributed residual phases, a homogeneous matrix, the highest compressive strength, and suitable conditions for subsequent aging, thus being identified as optimal. Fractography reveals a transition from quasi-cleavage in the as-cast state toward enhanced ductility after solution treatment. However, small cleavage facets after 10 h are attributed to stress concentrations from rare-earth-rich regions and reduced deformation compatibility due to retained LPSO phases. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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15 pages, 6377 KB

Open AccessArticle

Wear and Corrosion Resistance of Thermally Formed Decorative Oxide Layers on Austenitic Steel

by Tomasz Borowski, Hubert Wójcik, Maciej Spychalski and Bogusława Adamczyk-Cieślak

Metals 2025, 15(7), 707; https://doi.org/10.3390/met15070707 - 25 Jun 2025

Cited by 2 | Viewed by 975

Abstract

This article presents the results of tests on the functional properties of oxide layers (Fe₂O₃, Cr_1.3Fe_0.7O₃) produced on AISI 316L austenitic steel, which is susceptible to friction wear, using a new, simple, inexpensive, and environmentally friendly process conducted in air at three different temperatures (400 °C, 450 °C and 500 °C). Vickers microhardness tests showed that the process slightly increased hardness only at lower indenter loads, indicating a low thickness of the layers. The greatest increase in hardness was observed in the sample oxidized at the lowest temperature. Tests performed using an optical profilometer showed a tendency for surface roughness to increase with oxidation temperature. Low surface roughness, enhanced microhardness and a low coefficient of friction resulted in the steel oxidized at 400 °C exhibiting the lowest wear rate in the “ball-on-disc” test. The contact angle measurements for all tested samples indicated hydrophilic properties. Potentiodynamic tests showed a deterioration in the corrosion resistance of the steel after oxidation at 450 °C and 500 °C. Oxidation at 400 °C did not cause a significant decrease in pitting corrosion resistance, while an increase in polarization resistance and a decrease in corrosion current density were observed. An interesting phenomenon, requiring further research, is the greatest increase in hardness and wear resistance observed in the layer formed at 400 °C. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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13 pages, 4362 KB

Open AccessArticle

The Effect of N/O Elements on the Microstructure and Mechanical Properties of Ti-N-O Alloys

by Mingqi Shi, Ruiduo Chen, Chengsong Zhang, Zhenzhao Xu, Hanke Hu, Xiaolong Zhou and Guodong Cui

Metals 2025, 15(5), 554; https://doi.org/10.3390/met15050554 - 17 May 2025

Viewed by 1124

Abstract

A novel Ti-N-O composite was prepared by powder nitriding/oxynitriding combined with the spark plasma sintering (SPS) method. The effects of N/O on the microstructure and mechanical properties of the Ti-N-O alloy were systematically studied. The results showed that the addition of N/O elements significantly improved the mechanical properties of commercially pure titanium (cp-Ti). The hardness reached 298.8 HV0.1 while the yield strength can reach 666 MPa. And, the O element played a leading role in regulating the microstructure and morphology of the Ti-N-O alloy. With the addition of the O element, the microstructure showed an equiaxed structure, and the characterization showed that this region is an O-enriched region, and that a small amount of nano-TiO₂ particles appeared in the alloy, which together led to the change in the microstructure. At the same time, more large-angle grain boundaries were generated in the Ti-N-O alloy. This study investigated a new method for the preparation of titanium materials and provides new ideas for researching medical titanium materials. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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26 pages, 5867 KB

Open AccessArticle

On Transformation and Stress–Strain–Temperature Behavior of Fine-Grained Ni-Rich NiTi Wire vs. Aging Mode

by Elena Ryklina, Kristina Polyakova, Victor Komarov, Semen Murygin, Anton Konopatsky, Vladimir Andreev and Adilet Ulanov

Metals 2025, 15(1), 3; https://doi.org/10.3390/met15010003 - 25 Dec 2024

Cited by 2 | Viewed by 2689

Abstract

The present study was carried out using a cold-drawn wire of Ni_50.8Ti at.% subjected to post-deformation solution treatment at 700 °C for 1 h to obtain a fine-grained recrystallized structure. Subsequent aging was carried out at a temperature range of 300, 430, and 500 °C for 1, 10, and 20 h. The time–temperature aging mode strongly affects the aging-induced microstructure. Variation of the aging-induced microstructure (using various aging modes) permits precise tuning of the characteristic temperature of the martensitic transformations and their specific temperature ranges upon cooling and heating. The latent heat and hysteresis exhibit different evolution vs. aging durations; this finding remains fair when using different aging temperatures. The aging mode strongly affects the stress–temperature behavior: (i) a dramatical expansion of the temperature range of realization of the transformation yield stress (σ_tr); and (ii) the magnitude of σ_tr at a chosen test temperature is generally determined by the position of the M_s temperature. An additional contribution of competing factors is discussed. The efficiency of the aging temperature under isochronous aging is significantly higher than the efficiency of the aging time under isothermal aging. Aging at 430 °C for 10–20 h provides the highest resource for the recovery strain. The strain–temperature behavior strongly depends on the relative position of the R_s and M_s temperatures (onset of B2→R and R→B19′ transformations, respectively). The regularities obtained can be used to predict the set of functional and mechanical properties of titanium nickelide. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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16 pages, 20389 KB

Open AccessArticle

Analysis of the Structure and Properties of As-Built and Heat-Treated Wire-Feed Electron Beam Additively Manufactured (WEBAM) Ti–4Al–3V Spherical Pressure Vessel

by Andrey Chumaevskii, Sergey Tarasov, Denis Gurianov, Evgeny Moskvichev, Valery Rubtsov, Nikolay Savchenko, Aleksander Panfilov, Alexander M. Korsunsky and Evgeny Kolubaev

Metals 2024, 14(12), 1379; https://doi.org/10.3390/met14121379 - 2 Dec 2024

Cited by 4 | Viewed by 1476

Abstract

In the present work, a high-pressure spherical vessel was fabricated from Ti–4Al–3V titanium alloy using wire-feed electron beam additive manufacturing and characterized for tightness at high pressure. Studies have been carried out to characterize the microstructures and properties of the vessel’s material in four states: as-built (BM), annealed at 940 °C with cooling in air (HT₁ treatment), quenched in water from 940 °C (HT₂ treatment), and quenched with subsequent annealing at 540 °C (HT₃ treatment). The microstructure of the as-built (BM) samples was composed of grain boundary α-Ti and α/β lath colonies located within the columnar primary β-Ti grain boundaries. The ultimate tensile strength of the as-built material was in the range of 582 to 632 MPa, i.e., significantly lower than that of the source Ti–4Al–3V alloy wire. The subtransus HT₁ heat treatment allowed β→α″ transformation, while both HT₂ and HT₃ resulted in improved tensile strength due to the transformation of β-Ti into α/α′-Ti and the decomposition of α′ into α/β structures, respectively. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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14 pages, 12307 KB

Open AccessArticle

Phase Transformations after Heat Treating an As-Cast Fe-30Mn-8.8Al-0.3Si-0.15C Steel

by Victor M. Lopez-Hirata, Eduardo Perez-Badillo, Maribel Leticia Saucedo-Muñoz, Felipe Hernandez-Santiago and Jose David Villegas-Cardenas

Metals 2024, 14(7), 748; https://doi.org/10.3390/met14070748 - 25 Jun 2024

Cited by 4 | Viewed by 2078

Abstract

The phase transformations in an as-cast Fe-30Mn-8.8Al-0.3Si-0.15C steel were analyzed experimentally and numerically with a Calphad-based method during heat treatment. The nonequilibrium phases were determined using the Thermo-Calc Scheil module and the equilibrium phases with Themo-Calc based on the steel chemical composition. The precipitated phases were analyzed with TC-PRISMA using the chemical composition, nucleation site, and temperature among other factors. An ingot of this chemical composition was vacuum-melted using pure elements under an Ar gas atmosphere. As-cast steel specimens were annealed and solution-treated, quenched, and then aged at different temperatures. Heat-treated specimens were analyzed by different techniques. The results indicated that the microconstituents are the α and γ phases for the as-cast, homogenized, and quenched conditions. The main difference among these conditions is the distribution and size of the γ phase, which produced a change in hardness from 209 to 259 VHN. In contrast, the aging treatment at 750 °C caused a decrease in hardness from 492 to 306 VHN, which is attributable to the increase in volume fraction of the γ phase. On the other hand, the aging treatment at 550 °C promoted precipitation hardening from 259 to 649 VHN because of the κ precipitate formation. The calculated results for the different heat treatments with the Calphad-based method agreed well with the experimental ones. In addition, the intragranular precipitation of the κ phase could be simulated using the nucleation and growth and coarsening mechanisms based on a Calphad method. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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15 pages, 6616 KB

Open AccessArticle

Temperature Dependency of Modified Mohr–Coulomb Criterion Parameters for Advanced High Strength Dual-Phase Steel DP780

by Yukuan Li, Di Li, Hui Song, Yiqun Wang and Dongze Wu

Metals 2024, 14(6), 721; https://doi.org/10.3390/met14060721 - 17 Jun 2024

Cited by 3 | Viewed by 1830

Abstract

The Modified Mohr–Coulomb criterion has been demonstrated to exhibit high accuracy in the prediction of fracture in high-strength steels. Taking DP780 as the research object, the undetermined parameters of the Modified Mohr–Coulomb criterion at different temperatures were calibrated by tensile and shear tests combined with simulation. The relationships between the parameters and temperature were investigated. Finally, the relationship between criterion parameters and temperature was verified using the stretch-bending tests of U-shape parts. The fracture of automotive parts can be accurately predicted by simulation during warm stamping, thereby guiding actual production. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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