无序合金的序调控
2025, 74 (8): 086101.
doi: 10.7498/aps.74.20250097
Abstract +
2025, 74 (8): 086102.
doi: 10.7498/aps.74.20250128
Abstract +
Multi-principal element alloys (MPEAs), also known as high-entropy alloys (HEAs), are novel materials that have received significant attention due to their exceptional mechanical properties, thermal stability, and resistance to wear and corrosion. These alloys are typically composed of multiple principal elements in near-equal atomic proportions, forming solid solution phases such as face-centered cubic (FCC) or body-centered cubic (BCC) structures. Despite the promising applications, a more in-depth understanding of the atomic-level behavior, particularly, lattice distortion and atomic strain, is essential to better design and optimize these materials in extreme environments. This study focuses on systematically investigating the atomic-scale lattice distortion characteristics and their influence on atomic strain in three representative BCC-based MPEAs: TaWNbMo, TiZrNb, and CoFeNiTi. We utilize molecular dynamics (MD) simulations to explore the local atomic strain distributions in these alloys at various temperatures. Von Mises strain and volumetric strain are employed as key descriptors to quantify the atomic strain, providing a clear representation of how lattice distortion on an atomic scale influences the overall strain behavior. The study specifically addresses the effects of atomic radius differences, chemical short-range ordering, and temperature on the strain characteristics of the alloys. The results obtained indicate that an increase in lattice distortion corresponds to a broader distribution of von Mises strain and volumetric strain, with strain values significantly amplified. More precisely, alloys with larger atomic radius differences exhibit greater volumetric strain, reflecting the influence of atomic size disparity on strain distribution. Furthermore, the formation of chemical short-range order (CSRO) significantly mitigates lattice distortion and atomic strain. This finding highlights the importance of short-range atomic ordering in enhancing the stability of the alloy structures, thus potentially improving their mechanical properties. Temperature effects are also investigated, revealing that elevated temperature induces more intense atomic vibration, which in turn increases the atomic strain. The findings underscore the complex interplay between atomic-scale phenomena and macroscopic mechanical properties, offering new insights into the microscopic mechanical behavior of high-entropy alloys. This study contributes to a better understanding of the underlying mechanisms driving atomic strain and lattice distortion in MPEAs. The results provide valuable theoretical insights that can guide the design of high-performance alloys tailored for high-temperature and extreme environments. By addressing the key factors influencing atomic strain, such as atomic radius, chemical ordering, and temperature, this work lays the foundation for future research aimed at enhancing the mechanical performance of MPEAs in various industrial applications.
2025, 74 (8): 086103.
doi: 10.7498/aps.74.20250141
Abstract +
Medium-entropy alloys (MEAs), renowned for their outstanding strength and ductility, possess great potential for high strain-rate applications. This study focuses on a NiCoV-based MEA system, and proposes a novel alloy design strategy to fabricate the (NiCoV)95W5 alloy by introducing 5% (atomic percent) high-melting-point tungsten through vacuum arc melting coupled with thermomechanical processing. Split Hopkinson pressure bar (SHPB) experiments are conducted to elucidate the dynamic response mechanism and deformation behavior under high strain rates (2000－6000 s–1). The results show that due to severe lattice distortion, the enhanced phonon drag effect at elevated strain rates results in a substantial increase in yield strength from 720 MPa (10–3 s–1) to 1887 MPa (6000 s–1), an increase of 162%, accompanied by a relatively high strain-rate sensitivity (m = 0.42). Microscopic analysis reveals the multi-scale cooperative deformation mechanism of the alloy system under high strain rate. When the strain rate is 2000 s–1, the alloy exhibits a low dislocation density dominated by dislocation planar slip. As the strain rate increases to 4000 s–1, the increased flow stress and deformation promote the proliferation and entanglement of a large number of dislocations into high-density dislocation cells. The accumulation of dislocation stress leads to the coordinated deformation of precipitates and releases stress concentration at the phase interface. When the strain rate further increases to 6000–1, severe plastic deformation will lead to the formation of nanotwins within the matrix, which is the main strain hardening. This study elucidates the dynamic response mechanism of NiCoV MEA mediated by tungsten doping, providing a guidance for designing novel structural materials with excellent dynamic mechanical responses.
