Outer space provides unique environmental conditions for investigating the physical and chemical properties of metallic materials, the mechanisms of phase transformation processes, and the regulation of microstructure and performance. In particular, it has considerable scientific significance and application value for the preparation of high-temperature, highly active metallic materials, as well as for the implementation of in situ resource utilization and space manufacturing. This study reviews the main research on metallic materials conducted under space experimental conditions since the 1960s and summarizes the materials science experimental platforms and their main functions on the Chinese Space Station, the International Space Station, and the Mir Space Station. Research progress in aspects such as melt flow, liquid properties, solidification structure, and extravehicular exposure is analyzed. The special phenomena and new laws unveiled through space experiments are clarified. Finally, the research and development trends of metallic materials for space manufacturing are prospected.
The topological properties of metallic grain boundaries are crucial in determining their mechanical, electrical, and chemical behaviors, making them a major focus of grain boundary engineering. This study systematically reviews recent advancements in understanding the topological characteristics of metallic grain boundary structures at various scales, including atomic-scale topological configurations and mesoscale grain boundary network topology. It begins by summarizing current research on the topology of grain boundary atomic structures, including the coincidence site lattice model, displacement shift complete lattice theory, topological characterisation of grain boundary dislocation networks, and analysis of topological defects. It then introduces characterisation methods for mesoscale grain boundary networks, emphasising a research framework based on discrete cell complexes and systematically examining the topological properties of these networks. Finally, potential applications of grain boundary topology research in materials design are discussed.
TiAl alloys are important lightweight materials for aerospace propulsion systems owing to their low density, creep resistance, corrosion resistance, and other properties. Fatigue is the primary failure mode of aeroengine blades. Once a long crack forms in a blade, rapid fracture can occur. The initiation and propagation of small fatigue cracks therefore directly determine the service life of blades. Focusing on the issue of small fatigue cracks in TiAl alloys, this paper systematically reviews the definition and characteristics of small fatigue cracks and summarizes the mechanisms of crack initiation and propagation in TiAl alloys. In addition, the propagation models of small fatigue cracks, together with their applicability and limitations, are discussed. Finally, future perspectives are presented regarding the characterization of fatigue small-crack initiation and propagation behavior and the development of unified life prediction methods for TiAl alloys.
Aluminum matrix composites, due to their high specific strength and modulus, excellent thermal conductivity, and controllable thermal expansion coefficient, show prospective broad applications in aerospace, automotive, and electronic packaging. However, traditional single-scale reinforcements often enhance material strength while reducing plasticity and toughness. This strength-toughness trade-off limits further material development. This bottleneck can potentially be overcome through an approach based on the recently developed “cross-scale synergistically reinforcement” strategy, inspired by the multiscale structures of natural biological materials. By the synergistic combination of micron- and nano-scale reinforcements into multiscale structures, the strategy aims to simultaneously enhance strength, modulus, plasticity, and toughness. This paper systematically reviews the research progress on cross-scale synergistic reinforcement in aluminum matrix composites. Additionally, this paper elucidates the design philosophy of cross-scale synergy, discusses the primary material systems, key fabrication techniques, and underlying mechanisms of cross-scale synergistic reinforcement, and outlines future research directions. Finally, this paper aims to provide theoretical guidance for the design and development of high-performance aluminum matrix composites.
Extreme environments, such as ultra-high temperatures, extremely low temperatures, and intense irradiation, impose growing demands on structural materials for next-generation engineering applications. Conventional single-principal-element alloys are approaching their performance limits because of insufficient phase stability, low-temperature ductile-to-brittle transitions, and uncontrolled defect evolution. Conversely, high-entropy alloys (HEAs), characterized by multi-principal elements, exhibit high configurational entropy, severe lattice distortion, and chemical short-range order. These intrinsic characteristics enable exceptional thermal-mechanical stability, cryogenic toughness, and irradiation resistance, rendering them promising candidates for applications in extreme environments. Focusing on three representative conditions, this work summarizes the potentials and challenges of HEAs as structural materials, clarifies the underlying high-entropy-driven mechanisms, and identifies key technological barriers. Furthermore, we report perspectives on future research directions and propose pathways to accelerate the transition of HEAs from laboratory-scale research to practical engineering applications.
Solidification is a fundamental process in advanced manufacturing, playing a pivotal role in determining the microstructure and performance of components. Directional solidification is a critical technique for producing single-crystal superalloy components; however, precise control of dendritic structure remains challenging. This article aims to systematically review the current status and future trends of dendrite growth simulations in directional solidification. In addition, it seeks to elucidate the key role of multiscale modeling in predicting dendritic morphology, dendrite competition, and defect formation. This article focuses on dendritic growth and summarizes the constitutional undercooling theory, dendrite growth models, and typical directional solidification processes. Multiscale numerical simulation methods, including finite element, finite difference, cellular automaton, and phase-field approaches, are emphasized, with an analysis of their applicability and a discussion of their representative achievements from macroscopic physical-field simulation to microscopic dendrite growth modeling. Finally, the key challenges are outlined, and prospective advancements in the numerical simulation of dendrite growth in directional solidification are delineated.
Difficult-to-machine metals typically possess unique physical and mechanical properties, such as high-temperature stability, high specific stiffness, and lightweight characteristics. These metals hold strategic significance for high-end equipment sectors such as aerospace, energy and power, and marine engineering. This study systematically reviews the research progress and development trends in the integrated additive manufacturing/hot isostatic pressing (AM/HIP) forming technology for difficult-to-machine metals. The study focuses on the following four typical materials: (i) Be and its alloys, (ii) Ti2AlNb alloys, (iii) nickel-based superalloys with high Ti/Al content, and (iv) metal matrix composites. This study provides an in-depth analysis of the bottlenecks encountered in conventional processing, such as high forming difficulty, low material utilization, and poor microstructural homogeneity. Furthermore, the study highlights key research breakthroughs in the integrated AM/HIP technology, including multiscale HIP simulation, compensation design methods for capsule structures, AM of high-precision and high-density thin-walled capsules, and AM of high-strength soluble ceramic cores. A comparative analysis is performed on the advantages of the technology in the near-net shaping, microstructural homogenization, and performance optimization of components made from difficult-to-machine materials. Finally, future developments for the technology are outlined, including scientific capsule design, intelligent process control for capsule AM, and synergistic optimization of ceramic core properties. This study provides theoretical support and practical pathways to promote the innovative development of HIP forming technology, expanding its application in the near-final forming of complex components made from difficult-to-machine metals, and offering technical assistance for the manufacturing of core components in key sectors in China, such as aerospace and defense equipment.
In recent years, artificial intelligence-based computational materials modeling has advanced rapidly, with machine learning potentials (MLPs) emerging as a central research direction. By fitting ab initio reference data into continuous and differentiable functional forms, MLPs retain near-quantum-mechanical accuracy while substantially reducing computational cost. This capability alleviates the limitations of ab initio methods in simulations of large-scale systems and long timescales. Consequently, MLPs serve as a critical link between atomistic simulations and macroscopic material property predictions, enabling new possibilities in computational materials science. This review focuses on the moment tensor potential (MTP), which offers an excellent balance between accuracy and computational efficiency. This paper provides a systematic overview from three perspectives: theoretical framework, algorithmic optimization, and practical applications. First, the mathematical foundations and design principles of MTP are analyzed. Next, strategies for improving accuracy and accelerating computation are discussed. Finally, representative case studies on typical material systems are presented to demonstrate the performance of MTP, and future development directions are outlined.
Multiscale plasticity mechanics aims to reveal the plastic deformation response of materials across length scales and to establish physical links among the microstructure, deformation mechanisms, and macroscopic properties, providing critical insights for materials design and performance optimization. Plasticity in metallic materials often involves the interplay of multiple microstructures and deformation mechanisms such as dislocations, interfaces, and phase transformations, which together form a highly complex spatiotemporal system. Traditional modeling approaches struggle to handle configurational complexity, bridge different scales, or represent the underlying mechanisms in such systems. Recently, machine learning has been integrated with multiscale simulations and constitutive modeling, opening new avenues in multiscale plasticity research. This review focuses on two primary aspects of machine learning-enabled multiscale plasticity studies: multiscale simulations of plastic deformation and the development of constitutive models. Representative examples include machine learning-based interatomic potential construction, dislocation dynamics simulations, finite element simulations of crystal plasticity, and data-driven constitutive modeling. Finally, the review envisages future directions for multiscale plasticity mechanics empowered by machine learning.
Corrosion fatigue is a typical failure mode of metallic materials subjected to the combined effects of cyclic loading and corrosive environments. It is widely observed in critical fields such as nuclear power, marine engineering, aerospace, and energy equipment, and directly affects the service safety and life assessment of engineering components. With the advancement of advanced energy systems operating in extreme environments such as deep space, deep sea, and deep earth, materials increasingly experience severe environmental-mechanical coupling damage. Among these environments, high-temperature pressurized water, liquid lead-bismuth, and marine conditions represent typical corrosive systems. Therefore, understanding and predicting the corrosion fatigue behavior of metallic materials under these conditions is of considerable importance. This paper reviews recent research progress on corrosion fatigue experimental techniques, damage mechanisms, and prediction models for metallic materials in the three representative corrosive environments mentioned above. Regarding experimental techniques, particular attention is given to the development of fatigue testing devices capable of simulating service environments, as well as in situ monitoring methods for specimen strain/displacement and crack length. In terms of damage mechanisms, the competition and synergistic interactions among several mechanisms are discussed, including stress concentration at corrosion pits, rupture of protective films and slip dissolution, hydrogen ingress and hydrogen-induced damage, and reductions in surface energy. For prediction models, the evolution from traditional empirical models, such as the Basquin and Coffin-Manson models, to data-driven machine learning approaches is summarized. The limitations of current models in terms of engineering applicability and integration of physical mechanisms are also highlighted. Furthermore, this paper discusses major challenges in the field, including the lack of experimental techniques for emerging extreme environments, insufficient understanding of multimechanism coupled damage theories, and the absence of high-precision life prediction models under small-sample conditions. Future research directions are proposed, including the development of cross-scale in situ characterization techniques, the integration of physical mechanisms with machine learning methods, and the advancement of design and evaluation systems for materials resistant to corrosion fatigue.
Dissimilar material joining technologies play a critical role in enabling lightweight design and functional integration in complex structures and are widely applied in aerospace, equipment manufacturing, and transportation industries. However, significant differences in properties, such as thermal expansion coefficients, melting points, and metallurgical compatibility, pose major challenges. These disparities often result in poor interfacial bonding, the formation of excessive brittle intermetallic compounds, and high residual stresses within joints. This review summarizes major dissimilar material joining techniques, including brazing, diffusion bonding, friction stir welding, high-energy beam welding, and additive manufacturing, along with their applications in the fabrication of complex structures. Key scientific issues associated with these processes, such as interfacial bonding mechanisms, joint strengthening strategies, and structural reliability, are discussed, and future development trends are briefly outlined.
Continuous casting is a critical process in the modern iron and steel manufacturing industry. The solidification segregation of continuously cast strands largely affects the yield rate, performance, and service life of steel products. National strategic drives have imposed increasingly stringent demands on the requirements for iron and steel materials. So, macro- and meso-scopic segregation in the solidification of continuously cast strands has become increasingly prominent as the types of alloying elements increase and strand sections continue to be enlarged. This paper elaborates the segregation distribution characteristics in the transverse and longitudinal sections of continuously cast strands and clarifies the formation mechanisms of subsurface segregation, white banding, segregation in the columnar-to-equiaxed transition region, V-shaped segregation, and central/centerline segregation. It also analyzes the generation modes of melt flow and the mechanism of solute segregation cooperatively induced by the melt flow and solidification structure. The paper further identifies the main factors influencing different types of solute segregation and introduces the technical principles and development status of electromagnetic stirring and mechanical reduction. The importance of refining the solidification microstructure for homogenization control is emphasized. Finally, the paper outlines key research directions for high-homogenization control theories and technologies for ultralarge-section continuously cast strands of high-alloy steels, providing a reference for high-quality continuous casting production of base metals for large structural components.
Ni-based single crystal superalloys are key materials for turbine blades in aero-engines and gas turbines. Their deformation and damage behavior under the coupled effects of high temperature, complex stress states, and harsh environments directly affects blade service safety and lifespan. This paper systematically reviews recent research progress on single-crystal superalloys with respect to creep, fatigue, and thermo-mechanical fatigue (TMF), with an emphasis on the evolution of microstructures and damage mechanisms under multifield coupling conditions. For creep, the effects of thickness debit, hot corrosion, and multiaxial stress on material properties are summarized, and emerging phenomena and mechanisms associated with ultra-high-temperature exposure, long-term service, and nonisothermal creep are discussed. For fatigue, the transformation of crack initiation mechanisms under low-cycle, high-cycle, and very-high-cycle fatigue conditions is clarified; the synergistic effects of thermo-mechanical-environment coupling and multiaxial stress are examined; and the critical roles of surface condition and structural characteristics in component fatigue performance are highlighted. For TMF, the influences of phase relationship, crystal orientation, alloying elements, and coating-substrate interactions on damage behavior are reviewed. Additionally, this paper reviews the application and progress of in situ characterization techniques for elucidating deformation and damage mechanisms. Finally, future research directions in this field are outlined.
Magnesium alloys are widely employed in lightweight applications such as aerospace, transportation, and biomedical devices due to their low density, high specific strength, and good biocompatibility. Elucidating the dynamic evolution of microstructures during preparation and service is essential for alloy compositional design, processing optimization, and performance enhancement. Synchrotron radiation sources, which generate X-ray beams with high flux, high resolution, and high coherence, enable in situ dynamic characterization of microstructural evolution in magnesium alloys throughout the entire processing chain and under simulated service conditions. This paper briefly overviews the development of in situ sample environment devices at synchrotron facilities worldwide. It also systematically outlines recent research on the microstructural evolution mechanisms of magnesium alloys investigated using this advanced technology, covering solidification, deformation and damage, as well as corrosion and protection. Finally, future directions for the application of synchrotron radiation technology in magnesium alloy research are discussed.
Mo, a trace element in the human body, has attracted increasing attention owing to its excellent mechanical properties, uniform degradation behavior, and favorable biocompatibility. The highlighted features make it a promising candidate for various biodegradable medical devices, including cardiovascular and neurovascular stents, cardiac pacemakers, gastrointestinal anastomotic staples, and wearable bioelectronic devices. Currently, Mo and its alloys have been developed as industrial materials and are well-established in aerospace, electronics, and chemical engineering. However, research on Mo and its alloys as biomaterials is an emerging field of study and faces several critical scientific challenges. In this review, we highlight Mo's intrinsic material characteristics, summarize traditional manufacturing methods and performance advantages, and outline its degradation mechanisms and biological responses in physiological environments. Furthermore, we propose design strategies for Mo-based biodegradable metals that consider biodegradability, biocompatibility, and the functional requirements of biodegradable implants, focusing on composition, microstructure, plastic deformation, and additive manufacturing. Finally, we discuss the future applications and developmental directions of Mo-based biodegradable metals in the field of biomaterials.
Aluminum matrix composites (AMCs) can be widely employed across fields such as aerospace and transportation owing to their high-specific strength and modulus as well as excellent thermal and electrical conductivity. In situ reaction technology enables the formation of thermodynamically stable reinforcements within the Al matrix, resulting in clean interfaces and strong interfacial bonding that considerably enhance the overall mechanical properties of AMCs. Consequently, this technology has emerged as a pivotal approach for fabricating high-performance AMCs. This review aims to comprehensively elucidate the design principles, interface optimization, and performance regulation of powder metallurgy AMCs fabricated via in situ reactions, thereby promoting the development of a new generation of high-performance AMCs. Specifically, the reaction mechanisms as well as reinforcement types and characteristics in various in situ reaction systems developed via powder metallurgy are systematically investigated. In addition, the interfacial microstructure characteristics between in situ reinforcements and the Al matrix are examined, with particular emphasis on the influence of crystallographic orientation relationships on interfacial properties. Moreover, research progress in optimizing interfacial bonding via modification strategies is discussed, and the influence of interfacial structure on the mechanical properties of AMCs is summarized along with an outlook on future development directions.
High-pressure die casting (HPDC), characterized by high filling speeds and rapid solidification, has become a key manufacturing process for large integrated aluminum alloy structural components in electric vehicles. However, in large thin-walled castings, complex coupling exists between melt flow behavior and the evolution of microstructural defects, and the underlying mechanisms remain insufficiently understood. This paper systematically reviews recent progress in the fluidity of aluminum alloys under HPDC conditions and establishes a unified analytical framework from three perspectives: process parameters, microstructural characteristics, and analytical models. First, the factors influencing fluidity in die casting are summarized, highlighting that both processing parameters and alloy design jointly affect fluidity by regulating heat transfer and solidification processes. Second, the formation mechanisms of the characteristic layered microstructure in die castings, including the skin layer, defect band, and externally solidified crystals (ESCs), are elucidated. The critical roles of dendritic network connectivity, solute enrichment, and pore evolution in flow stoppage are also discussed. Finally, the differences among various analytical models for fluidity are compared in terms of their physical assumptions and predictive capabilities. Overall, the fluidity of die cast alloys is governed by the coupled interactions of thermal, phase transformation, and flow fields. Future research should further focus on the mechanisms of flow stoppage, in situ synchrotron characterization, and data-driven approaches.
Press-hardening steel offers numerous advantages, such as exceptional strength, excellent formability, and the ability to produce complex geometries, making it an essential material for lightweight, high-performance structures in new-energy vehicles. Press-hardening steel is widely used in manufacturing safety components for vehicles. With the escalating demand for lightweight components in the automotive industry, press-hardening steel is evolving toward enhanced strength, ductility, and fracture toughness. However, alongside technological advancements, the challenges faced by press-hardening steel in terms of low bending toughness and hydrogen embrittlement are becoming increasingly severe. This review summarizes the current state and future prospects of press-hardening steel from three key perspectives. Firstly, it describes the press-hardening process and the development of advanced materials with enhanced strength and toughness. Secondly, it reviews recent research on toughening commercial press-hardening steels, examining the interplay between surficial steel coatings and cold-bending-angle standards, addressing the structural limitations of current products, and highlighting future advancements in coatings. Lastly, the paper summarizes the latest research on hydrogen embrittlement in press-hardening steel, starting with the underlying mechanisms of hydrogen-induced damage, while considering factors such as the internal microstructure and surface coating conditions of the steel. The paper concludes by outlining research directions for developing higher-strength press-hardening steels with improved resistance to hydrogen embrittlement.
Strain path is a critical factor governing the forming quality of metallic components, including their geometry, microstructure, and service performance. Achieve high-quality forming often requires the use of nonlinear and complex strain paths, which inevitably give rise to multiscale deformation behaviors. Understanding and characterizing these mechanisms has therefore become a frontier topic in the field of plastic forming. This review synthesizes recent advances in the investigation of macroscopic mechanical responses, damage behavior, and microstructural and textural evolutions under complex strain paths, emphasizing the central role of stress path history in shaping multiscale deformation mechanisms. Finite element modeling strategies that account for strain path effects are discussed, including constitutive models, limit prediction and damage models, as well as microstructure evolution models, with particular attention to their roles in improving predictive accuracy and process simulation capabilities. Engineering-oriented approaches to strain path design are also summarized, highlighting their potential for optimizing formability and service performance. Finally, perspectives on future research directions are presented.
