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Crystals
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Investigation of Microstructural and Properties of Steels and Alloys
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Investigation of Microstructural and Properties of Steels and Alloys

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: 10 July 2026 | Viewed by 3202

Special Issue Editors

Dr. Saurabh Tiwari

E-Mail Website
Guest Editor
School of Materials Science and Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea
Interests: alloy design; phase transformations; structure–property relationships; advanced characterization; nanomaterials; steels; machine learning
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Marek Sroka

E-Mail Website
Guest Editor
Department of Engineering Materials and Biomaterials, Mechanical Engineering Faculty, Silesian University of Technology, ul. Konarskiego, 18a, 44-100 Gliwice, Poland
Interests: steel; alloys; mechanical properties; mechanical properties; precipitates; microstructure; welded joints, creep; heat treatment
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue focuses on recent advances in the understanding of microstructural characteristics and property relationships in steels and alloys. The collection aims to bring together cutting-edge research exploring the correlation between processing techniques, resulting microstructures, and the subsequent mechanical, thermal, and chemical properties of various steel grades and metallic alloys. 

Topics of interest include novel characterization methods, computational modeling of microstructural evolution, advanced processing techniques for microstructural refinement, phase transformation mechanisms, and strategies for enhancing properties. 

The issue welcomes original research articles, comprehensive reviews, and case studies that contribute to the fundamental understanding and practical applications of microstructure-property relationships in industrial and structural materials. This collection will serve as a valuable resource for metallurgists, materials scientists, mechanical engineers, and industrial researchers working on the development and optimization of high-performance steels and alloys.

Dr. Saurabh Tiwari
Prof. Dr. Marek Sroka
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • high-temperature alloys
  • Ni-/Co-based superalloys
  • steels
  • alloy design
  • nanomaterials
  • structure-property relationships
  • advanced microscopy
  • machine learning in materials science

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Published Papers (5 papers)

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Research

29 pages, 4522 KB  
Article
Machine Learning-Driven Prediction of Microstructural Evolution and Mechanical Properties in Heat-Treated Steels Using Gradient Boosting
by Saurabh Tiwari, Khushbu Dash, Seongjun Heo, Nokeun Park and Nagireddy Gari Subba Reddy
Crystals 2026, 16(1), 61; https://doi.org/10.3390/cryst16010061 - 15 Jan 2026
Viewed by 234
Abstract
Optimizing heat treatment processes requires an understanding of the complex relationships between compositions, processing parameters, microstructures, and properties. Traditional experimental approaches are costly and time-consuming, whereas machine learning methods suffer from critical data scarcity. In this study, gradient boosting models were developed to [...] Read more.
Optimizing heat treatment processes requires an understanding of the complex relationships between compositions, processing parameters, microstructures, and properties. Traditional experimental approaches are costly and time-consuming, whereas machine learning methods suffer from critical data scarcity. In this study, gradient boosting models were developed to predict microstructural phase fractions and mechanical properties using synthetic training data generated from an established metallurgical theory. A 400-sample dataset spanning eight AISI steel grades was created based on Koistinen–Marburger martensite kinetics, the Grossmann hardenability theory, and empirical property correlations from ASM handbooks. Following systematic hyperparameter optimization via 5-fold cross-validation, gradient boosting achieved R2 = 0.955 for hardness (RMSE = 2.38 HRC), R2 = 0.949 for tensile strength (RMSE = 87.6 MPa), and R2 = 0.936 for yield strength, outperforming the Random Forest, Support Vector Regression, and Neural Networks by 7–13%. Feature importance analysis identified the tempering temperature (38.4%), carbon equivalent (15.4%), and carbon content (13.0%) as the dominant factors. Model predictions demonstrated physical consistency with the literature data (mean error of 1.8%) and satisfied the fundamental metallurgical relationships. This methodology provides a scalable and cost-effective approach for heat treatment optimization by reducing experimental requirements based on learning curve analysis while maintaining prediction accuracy within the measurement uncertainty. Full article
(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)
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10 pages, 3852 KB  
Article
Influence of Silicon Content on Mechanical and Tribological Properties of FeSi Steels
by Marcela Motýľová, Ivan Petrišinec, Róbert Džunda and Jana Andrejovská
Crystals 2025, 15(12), 1005; https://doi.org/10.3390/cryst15121005 - 22 Nov 2025
Viewed by 502
Abstract
Non-oriented (NO) Fe–Si electrical steels are key materials for magnetic cores of electrical machines, requiring a balance between magnetic and mechanical properties. This study systematically examined the effect of silicon content (1.06 wt%, 2.15 wt%, and 3.09 wt%) on the microstructure, mechanical, and [...] Read more.
Non-oriented (NO) Fe–Si electrical steels are key materials for magnetic cores of electrical machines, requiring a balance between magnetic and mechanical properties. This study systematically examined the effect of silicon content (1.06 wt%, 2.15 wt%, and 3.09 wt%) on the microstructure, mechanical, and tribological behavior of three produced NO steel grades. Mechanical properties were assessed using tensile tests, microhardness, and nanoindentation, while tribological performance was evaluated under dry reciprocating sliding (ball-on-flat) against a 100Cr6 steel ball at loads of 5 N, 10 N, and 25 N. Increasing silicon content led to larger grain size, higher hardness (227 HV–361 HV) and strength, but lower ductility. Tribological behavior depended on both composition and load. The most stable friction regime occurred at 10 N. The medium-Si steel (N3, 2.15 wt%) exhibited the best performance with a low coefficient of friction (COF ≈ 0.52–0.55); N5 (3.09 wt%) showed a similar COF, while N1 (1.06 wt%) had a slightly higher value. At 25 N, an inverse relationship between hardness and friction appeared: softer N1 had the lowest COF (≈0.68–0.70), whereas harder N3 and N5 reached ≈ 0.74–0.78. Scanning electron microscopy (SEM) observations revealed abrasive wear for N3/N5 and plastic flow (galling) for N1. Overall, an optimal silicon content provides the best compromise between hardness and tribological stability depending on load conditions. Full article
(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)
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15 pages, 8005 KB  
Article
Effect of the Activator B(OCH3)3 on the Microstructure and Mechanical Properties of Cu-Mn-Al Alloy Coating via CMT Cladding
by Jin Peng, Shihua Xie, Junhai Xia, Xingxing Wang, Zenglei Ni, Pei Wang and Nannan Chen
Crystals 2025, 15(10), 881; https://doi.org/10.3390/cryst15100881 - 13 Oct 2025
Cited by 8 | Viewed by 549
Abstract
This study investigates the fabrication of a Cu-Mn-Al alloy coating on 27SiMn steel using Cold Metal Transfer (CMT) technology with an innovative Ar-B(OCH3)3 mixed shielding gas, focusing on the effect of the gas flow rate (5–20 L/min). The addition of [...] Read more.
This study investigates the fabrication of a Cu-Mn-Al alloy coating on 27SiMn steel using Cold Metal Transfer (CMT) technology with an innovative Ar-B(OCH3)3 mixed shielding gas, focusing on the effect of the gas flow rate (5–20 L/min). The addition of B(OCH3)3 was found to significantly enhance process stability by improving molten pool wettability, resulting in a wider cladding layer (6.565 mm) and smaller wetting angles compared to pure Ar. Macro-morphology analysis identified 10 L/min as the optimal flow rate for achieving a uniform and defect-free coating, while deviations led to oxidation (at low flow) or spatter and turbulence (at high flow). Microstructural characterization revealed that the flow rate critically governs phase evolution, with the primary κI phase transforming from dendritic/granular to petal-like/rod-like morphologies. At higher flow rates (≥15 L/min), increased stirring promoted Fe dilution from the substrate, leading to the formation of Fe-rich intermetallic compounds and distinct spherical Fe phases. Consequently, the cladding layer obtained at 10 L/min exhibited balanced and superior properties, achieving a maximum shear strength of 303.22 MPa and optimal corrosion resistance with a minimum corrosion rate of 0.02935 mm/y. All shear fractures occurred within the cladding layer, demonstrating superior interfacial bonding strength and ductile fracture characteristics. This work provides a systematic guideline for optimizing shielding gas parameters in the CMT cladding of high-performance Cu-Mn-Al alloy coatings. Full article
(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)
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17 pages, 5028 KB  
Article
Mechanical and Corrosion Properties of Ultrafine-Grained TC4-0.55Fe Alloy Processed by Equal-Channel Angular Pressing
by Yumeng Guo, Yu Lu, Miaoxia He, Yu Wang, Yuecheng Dong and Igor V. Alexandrov
Crystals 2025, 15(9), 795; https://doi.org/10.3390/cryst15090795 - 8 Sep 2025
Viewed by 749
Abstract
This study investigates the effects of multi-pass Equal-Channel Angular Pressing (ECAP) on the mechanical and corrosion properties of TC4-0.55Fe alloy through room-temperature tensile tests, electrochemical experiments, SEM, and EBSD characterization. The results demonstrate that, with increasing ECAP passes, the average grain size is [...] Read more.
This study investigates the effects of multi-pass Equal-Channel Angular Pressing (ECAP) on the mechanical and corrosion properties of TC4-0.55Fe alloy through room-temperature tensile tests, electrochemical experiments, SEM, and EBSD characterization. The results demonstrate that, with increasing ECAP passes, the average grain size is progressively refined from the initial 3.8 μm to 1.8 μm after four passes. After four passes, the yield strength and ultimate tensile strength increase from initial values of 906 MPa and 939 MPa to 995 MPa and 1022 MPa, respectively, while the elongation at fracture slightly decreases to 12.0%. Electrochemical corrosion results reveal that ECAP processing significantly enhances the corrosion resistance of the TC4-0.55Fe alloy. Specifically, the two-pass specimen exhibits nearly an order-of-magnitude reduction in both corrosion rate and self-corrosion current density compared to the initial state. The simultaneous improvement in strength and corrosion resistance is primarily attributed to the synergistic effects of grain refinement, increased dislocation density, and the evolution of basal texture. Full article
(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)
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24 pages, 13784 KB  
Article
Effect of Cold Rolling on Microstructure Evolution and Mechanical Properties of Zn-3Cu-1Mg-0.3Nd Alloy
by Huan Liu, Zhenghan Yang, Zhangwei Yang, Yuna Wu and Jia Ju
Crystals 2025, 15(9), 769; https://doi.org/10.3390/cryst15090769 - 29 Aug 2025
Cited by 4 | Viewed by 922
Abstract
Biodegradable zinc alloys for orthopedic implants must balance mechanical strength and plasticity, yet current as-cast alloys struggle to meet this dual requirement. In this study, a Zn-3Cu-1Mg-0.3Nd alloy was designed, and the influence of room-temperature rolling at four reduction levels (50%, 60%, 70%, [...] Read more.
Biodegradable zinc alloys for orthopedic implants must balance mechanical strength and plasticity, yet current as-cast alloys struggle to meet this dual requirement. In this study, a Zn-3Cu-1Mg-0.3Nd alloy was designed, and the influence of room-temperature rolling at four reduction levels (50%, 60%, 70%, and 80%) on its microstructure and mechanical properties was systematically investigated. Results indicate that as the reduction increases, the CuZn5 phase elongated along the rolling direction, and the η-Zn+Mg2Zn11 eutectic structure was progressively fragmented. The average grain size of the η-Zn matrix decreased significantly from 18.9 μm (50% reduction) to 1.71 μm (80% reduction). A distinct bimodal heterogeneous microstructure (coarse/fine grains) was formed at 60% and 70% reductions, while a predominantly fine-grained structure (91.3% fine grains) was achieved at 80% reduction. Furthermore, cracks initiated in the NdZn11 phase due to stress concentration during rolling. As the rolling reduction increases, the alloy’s ultimate tensile strengths (UTS) initially rose and then declined (peaking at 417 ± 5 MPa at 60% reduction), while its elongation (EL) consistently improved. At 80% reduction, the alloy exhibited optimal mechanical properties, achieving a tensile strength of 406 ± 4 MPa and an EL of 16.4 ± 0.3%, both significantly higher than those of the as-cast alloy (126 MPa, 4.4%). The enhancement in strength is attributed to a multi-scale synergistic mechanism involving grain refinement and back stress strengthening induced by heterogeneous microstructures. The continuous improvement in plasticity results from grain refinement, texture weakening, and the activation of non-basal <c+a> slip systems. Notably, cracks within the NdZn11 phase were confined by its high-binding-strength interface, preventing detrimental propagation into the matrix. This study elucidates the strengthening and toughening mechanisms in zinc alloys through cold rolling and the addition of the Nd element, particularly in terms of microstructural control and crack passivation, offering theoretical guidance for the design of biodegradable zinc alloy materials. Full article
(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)
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