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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Crystallography and Applications of Metallic Materials".

Deadline for manuscript submissions: closed (10 February 2026) | Viewed by 17166

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Dr. Cai Chen

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Sino-French Engineer School, Nanjing University of Science and Technology, Nanjing, China
Interests: crystallographic structures; crystallographic textures; FCC; BCC; HCP
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Special Issue Information

Dear Colleagues,

The microstructure and mechanical properties of metallic materials are fundamentally determined by their crystallographic structures and related orientations. The theoretical framework of metal crystallography serves as a cornerstone for understanding the physical and chemical properties of these materials. Over recent decades, the structure variation and characteristics of crystals have been extensively revealed to explain the properties of metallic materials. With the continuous advancement of material characterization techniques, research in metal crystallography has made significant progress, providing a solid theoretical foundation for the design and fabrication of high-performance metallic materials. Moreover, the design strategy of crystallographic structures is being increasingly recognized as a crucial method for achieving high performance in metallic materials.

Therefore, the content of this Special Issue, “Research Progress of Crystal in Metallic Materials”, focuses on the latest developments in the crystallography-related research of metallic materials. We are interested in metallic materials with various crystallographic structures, including FCC, BCC, and HCP. This Special Issue places particular emphasis on the latest characterization technologies, computational simulation methods, and theories in material crystallography. It aims to provide a dedicated platform for sharing past achievements and exploring future directions in the field of crystallography in metallic materials. We welcome relevant review articles and original research articles through experimental techniques or theoretical approaches.

Dr. Cai Chen
Guest Editor

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Keywords

crystallographic structures
crystallographic textures
FCC
BCC
HCP

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Published Papers (10 papers)

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Research

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13 pages, 3650 KB

Open AccessArticle

Formation Mechanisms of Chilled Layer on the Perimeter of Superalloy Seed

by Yangpi Deng, Dexin Ma, Jianhui Wei, Yunxing Zhao, Lv Li, Bowen Cheng and Fuze Xu

Metals 2026, 16(1), 79; https://doi.org/10.3390/met16010079 - 11 Jan 2026

Viewed by 194

Abstract

The seeding technique is the only way to precisely control the crystal orientation of single-crystal superalloy castings. However, an inevitable assembly gap exists between the seed and the mold cavity in practice, whose role in defect formation remains insufficiently understood. To elucidate the mechanism and impact of this gap, superalloy seeds were machined to different extents, aiming to create varying gaps with the mold. After the seeding experiment, the chilled layers formed on the perimeter of the pre-processed seeds were detected, exhibiting two distinct microstructural zones: a eutectic aggregation region at the bottom and an equiaxed grain at the top. The thicker the layer, the more pronounced the differences in microstructure between these two regions. This can be explained by the fact that during preheating, the γ/γ′ eutectic-rich interdendritic region (enriched with Al + Ti + Ta) in the original seed melted first due to its lower melting point. The molten fluid flowed downward into the gap, solidifying rapidly into the chilled layer. The leading portion of the fluid, melting from the interdendritic zone, formed the eutectic zone in the lower part of the chilled layer. The subsequently poured charge alloy melt (non-enriched with Al + Ti + Ta) generated the upper equiaxed zone with only a little γ/γ′ eutectic. These equiaxed grains in the chilled layer subsequently grew upward and potentially developed into stray grains of the casting. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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16 pages, 3563 KB

Open AccessArticle

Multiple Diffraction in a Basic Co-Rich Decagonal Al-Co-Ni Quasicrystal

by Changzeng Fan

Metals 2025, 15(12), 1386; https://doi.org/10.3390/met15121386 - 18 Dec 2025

Viewed by 470

Abstract

To reveal its influence on quasicrystal structure analysis, multiple diffraction effects in a basic Co-rich decagonal Al-Co-Ni quasicrystal have been investigated in-house and with synchrotron radiation. Two weak reflections were chosen as the main reflections in the in-house measurements, and 40°

ψ

-scans [...] Read more.

ψ

-scans of one main reflection have been performed with synchrotron radiation. As well as being known for periodic crystals and the icosahedral quasicrystal, it is also observed for this decagonal quasicrystal that the intensity of the main reflection may significantly increase if the simultaneous and the coupling reflections are both strong. The occurrence of multiple diffraction events during collection of a full data set as well as the

ψ

-scans measurements have been studied based on an average structure model and the kinematical multiple diffraction theory. The present experimental and simulation efforts on the effects of multiple diffraction suggest that it is insufficient on its own to explain the discrepancy in weak-reflection intensities; alternative explanations like the phasonic disorder should be paid more attention in future. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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15 pages, 2803 KB

Open AccessArticle

Analysis of the Regulatory Effect of Semi-Solid Isothermal Treatment Time on Crystallization and Plasticity of Amorphous Composites

by Xinhua Huang, Guang Wang, Bin Chen, Chenghao Wei, Jintao Zhao, Longguang Wu, Qi Li and Yuejun Ouyang

Metals 2025, 15(12), 1363; https://doi.org/10.3390/met15121363 - 11 Dec 2025

Viewed by 298

Abstract

Ti₄₈Zr₂₇Cu₆Nb₅Be₁₄ amorphous composites were prepared by copper mold suction casting to obtain as-cast specimens. Subsequently, the as-cast specimens were held at 900 °C for different durations (5, 10, 20, 30, and 40 min) and then water quenched to cool, yielding treated specimens. Room-temperature compression tests were conducted to characterize the mechanical properties of the materials before and after the treatment. X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) were used to detect and observe the microstructure of the specimens (before and after treatment) as well as the morphology of the side surface of compressed fractured specimens. Results show that the as-cast specimens are amorphous matrix composites, with dendrites (identified as β-Ti) predominantly distributed in the amorphous matrix. When the treatment duration increased from 5 to 40 min, two key phenomena were observed. The dendrites gradually disappeared and evolved into curved crystals first; subsequently, the curved crystals transformed into elongated crystals. Finally, the elongated crystals evolved into short and thick rod-like crystals, which further transformed into near-spherical crystals or spherical crystals. Furthermore, as the treatment duration prolonged, the average equivalent size of the crystals increased continuously, reaching 23.1 μm. Additionally, the plasticity of the specimens first increased, reached a maximum value of 16.2% when held for 30 min, and then decreased. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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28 pages, 5475 KB

Open AccessArticle

A Deep Learning-Based CNN-LSTM Framework for Constitutive Parameter Inversion in Alloy Gradient-Grained Materials

by Hao Jiang, Mengyi Chen, Jianxin Hou, Zhenfei Guo, Zixuan Hu, Zongzhe Man, Xiao Wei and Da Liu

Metals 2025, 15(12), 1286; https://doi.org/10.3390/met15121286 - 24 Nov 2025

Viewed by 648

Abstract

Alloy gradient-grained structures (represented by copper as a typical single-phase face-centered cubic (FCC) metal), known for their superior mechanical properties such as enhanced strength, ductility, and fatigue resistance, have become increasingly important in aerospace and automotive industries. These alloys are often fabricated using advanced processing techniques such as laser welding, electron beam melting, and controlled cooling, which induce spatial gradients in grain size and optimize material properties by overcoming the traditional strength–ductility trade-off. In this study, a deep learning-based inversion framework combining Convolutional Neural Networks (CNN) and Long Short-Term Memory (LSTM) networks is proposed to efficiently predict key constitutive parameters, such as the initial critical resolved shear stress and hardening modulus, in alloy gradient-grained structures. The model integrates spatial features extracted from strain-field sequences and grain morphology images with temporal features from loading sequences, providing a comprehensive solution for path-dependent mechanical behavior modeling. Trained on high-fidelity Crystal Plasticity Finite Element Method (CPFEM) simulation data, the proposed framework demonstrates high prediction accuracy for the constitutive parameters. The model achieves an error margin of less than 5%. This work highlights the potential of deep learning techniques for the efficient and physically consistent identification of constitutive parameters in alloy gradient-grained structures, offering valuable insights for alloy design and optimization. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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13 pages, 2211 KB

Open AccessArticle

Effect of Nickel Alloying on the Glass-Forming Ability and Corrosion Resistance of a Pt-Pd-Cu-P Bulk Metallic Glass

by Peiyun Ao, Su Song, Haiyong Liu, Lei Liu and Luliang Liao

Metals 2025, 15(11), 1188; https://doi.org/10.3390/met15111188 - 25 Oct 2025

Viewed by 664

Abstract

This study systematically investigates the effect of substituting Copper (Cu) with Nickel (Ni) on the glass-forming ability (GFA) and corrosion resistance of a Pt-based bulk metallic glass (BMG). We demonstrate that a minor substitution of 5 at.% Ni for Cu in the Pt₄₀Pd₂₀Cu₂₀P₂₀ base alloy significantly enhances both properties. The GFA is markedly improved, as evidenced by the supercooled liquid region (ΔTx) widening from 68 K to 91 K. The optimized Pt₄₀Pd₂₀Cu₁₅Ni₅P₂₀ alloy exhibits a compressive fracture strength of 1.38 GPa. Electrochemical tests in a 3.5 wt.% NaCl solution reveal a substantial improvement in corrosion resistance. Compared to the Ni-free baseline alloy, the passive film resistance (R_f) and charge-transfer resistance (R_ct) of the Ni-containing alloy are enhanced by factors of 2.75 and 2.60, respectively. This superior performance is attributed to a synergistic effect wherein Ni alloying both stabilizes the amorphous structure and promotes the formation of a more robust passive film. This work presents a viable strategy for designing cost-effective, high-performance multi-component BMGs for applications in aggressive chloride environments. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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21 pages, 35135 KB

Open AccessArticle

Effects of Post-Treatment on the Microstructure Evolution and High-Temperature Oxidation Properties of Nickel-Based Superalloys Fabricated by Selective Laser Melting

by Rui Ren, Yunxia Yao, Dongsheng Han, Jun Fang and Cai Chen

Metals 2025, 15(7), 708; https://doi.org/10.3390/met15070708 - 26 Jun 2025

Viewed by 1036

Abstract

This study mainly investigates the high-temperature oxidation properties of GH3230 alloys fabricated by selective laser melting after different heat treatments. The SLM-formed GH3230 samples were subjected to solid-solution treatments at 1100 °C, 1230 °C, and 1320 °C for 30 min, followed by water quenching to room temperature. High-temperature oxidation tests were conducted at 1100 °C for 100 h. The results show that the as-built sample is composed of many columnar grains with cellular dendrites. Many M₂₃C₆ carbides are distributed in the interdendritic of the as-built sample. After solid-solution treatment, the dendrite structures completely disappear and the M₂₃C₆ carbides are transformed into M₆C carbides. The M₆C carbides dissolve completely as the solid-solution temperature increases to 1320 °C. The average grain size of GH3230 samples increased gradually with the increase in the solid-solution treatment temperature. However, the degree of recrystallization increased with the heat treatment temperature, leading to the transformation of low-angle grain boundaries into high-angle grain boundaries. A relatively dense oxide film, mainly including Cr₂O₃ and CrMn₂O_4, are formed in the GH3230 alloy after high-temperature oxidation. Suitable solid-solution treatment improves the high-temperature oxidation resistance of the GH3230 alloy, and the enhanced oxidation-resistance mechanisms are discussed. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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15 pages, 5752 KB

Open AccessArticle

The Influence of Interface Morphology on the Mechanical Properties of Binary Laminated Metal Composites Fabricated by Hierarchical Roll-Bonding

by Yuanyuan Tan, Qingsong Mei and Xu Luo

Metals 2025, 15(6), 580; https://doi.org/10.3390/met15060580 - 23 May 2025

Cited by 2 | Viewed by 1164

Abstract

The interface morphology plays an important role in the mechanical properties of laminated metal composites (LMCs). In this study, binary LMCs with different crystallographic characteristics, namely Fe/Al (BCC/FCC), Ni/Al (FCC/FCC), and Mg/Al (HCP/FCC), were fabricated through the hierarchical roll-bonding process. The influence of interface morphology on the mechanical properties of the binary LMCs was investigated systematically. The results show that the strength–hardness coefficient (R) decreases with increasing interface morphology factor (α) for the LMCs, indicating that the strengthening effect of LMCs decreases with increased curvature of the interface. The experimental results reveal that α increases with the increase in rolling deformation (thickness reduction) for the LMCs, which is consistent with the finite element simulation results. The dependence of mechanical properties on interface morphology is mainly related to the microstructural inhomogeneity caused by localized deformation in the harder layer, including the formation of shear bands and variations in grain morphology, size, and orientation, which can lead to stress concentration in the necking zone. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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14 pages, 5541 KB

Open AccessArticle

Dendrite Structure Refinement and Mechanical Property Improvement of a Single-Crystal Superalloy

by Hongyuan Sun, Dexin Ma, Yunxing Zhao, Jianhui Wei, Xiaoyi Gong and Zhongyuan Sun

Metals 2025, 15(3), 295; https://doi.org/10.3390/met15030295 - 7 Mar 2025

Viewed by 1764

Abstract

In the present work, the effect of different casting processes on the microstructure and creep properties of the second-generation single-crystal superalloy DD419 was investigated. Under conventional production conditions and a contour-suited thermal insulation method, single-crystal rods of types A and B were fabricated, respectively. In comparison to rod type A, the solidification process of rod type B featured a 1.6-fold increase in the temperature gradient and a 32% reduction in primary dendrite spacing. The γ/γ′ eutectic in the as-cast microstructure, the residual eutectic phase, and porosity after heat treatment were also significantly reduced, resulting in the improved homogeneity of the single crystal castings. Under the testing conditions of 850 °C/650 MPa and 1050 °C/190 MPa, the stress rupture life of sample B was enhanced by 25% and 5.2%, respectively, compared to sample A. Therefore, due to dendrite structure refinement, the stress rupture life of the superalloy was evidently improved, especially at medium temperatures. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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18 pages, 6401 KB

Open AccessArticle

Finite Element and Machine Learning-Based Prediction of Buckling Strength in Additively Manufactured Lattice Stiffened Panels

by Saiaf Bin Rayhan, Md Mazedur Rahman, Jakiya Sultana, Szabolcs Szávai and Gyula Varga

Metals 2025, 15(1), 81; https://doi.org/10.3390/met15010081 - 17 Jan 2025

Cited by 10 | Viewed by 3390

Abstract

The current research aimed to investigate the critical buckling load of a simply supported aerospace-grade stiffened panel made of additively manufactured cubic lattice unit cell arrays, namely simple cubic, face-centered cubic (FCC) and body-centered cubic (BCC) structures. Ansys Design Modeler was chosen to design and analyze the critical buckling load of the panel, while a popular material, Ti-6Al-4V, was used as the build material. Numerical validation on both the stiffened panel and a lattice beam structure was established from multiple resources from the literature. Finally, the panels were tested against increments of a strut diameter ranging from 0.5 mm to 2 mm, which corresponds to a relative density of 6% to 78%. It was found that considering the relative density and fixed relative density, the simple cubic lattice cell outperformed the buckling results of the FCC and BCC panels. Moreover, the relationship of the parameters was found to be non-linear. Finally, the data samples collected from numerical outcomes were utilized to train four different machine learning models, namely multi-variable linear regression, polynomial regression, the random forest regressor and the K-nearest neighbor regressor. The evaluation metrics suggest that polynomial regression provides the highest accuracy among all the tested models, with the lowest mean squared error (MSE) value of 0.0001 and a perfect

R^{2}

score. The current research opens up the discussion of using cubic lattice cells as potential structures for future stiffened panels. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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Review

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29 pages, 18120 KB

Open AccessReview

Mechanical Properties and Strengthening Mechanisms of FCC-Based and Refractory High-Entropy Alloys: A Review

by Shuohong She, Chengxi Wang, Ming Chen and Vincent Ji

Metals 2025, 15(3), 247; https://doi.org/10.3390/met15030247 - 26 Feb 2025

Cited by 13 | Viewed by 6582

Abstract

The excellent mechanical properties of high-entropy alloys, especially under harsh service environments, have attracted increasing attention in the last decade. FCC-based and refractory high-entropy alloys (HEAs) are the most extensively used series. However, the strength of FCC-base HEAs is insufficient, although they possess a great ductility and fracture toughness at both room and low temperatures. With regard to the BCC-based refractory HEAs, the unsatisfactory ductility at room temperature shadows their ultrahigh strength at room and high temperatures, as well as their excellent thermal stability. In order to strike a balance between strength and toughness, strengthening mechanisms should be first clarified. Therefore, typical mechanical performance and corresponding strengthening factors are systemically summarized, including the solid solution strengthening, second phase, interface, and synergistic effects for FCC-base HEAs, along with the optimization of principal elements, construction of multi-phase, the doping of non-metallic interstitial elements, and the introduction of kink bands for refractory HEAs. Among which the design of meta-stable structures, such as chemical short-range order, and kink bands has been shown to be a promising strategy to further improve the mechanical properties of HEAs. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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