摘要
Understanding and controlling pressure-related structural transformations, which can be utilized to tune functional and mechanical properties of materials, is one of the most important research themes in materials science. However, the underlying mechanism governing pressure-driven phase transformations in high-entropy alloys (HEAs) remains poorly understood. By combining an in situ high-energy X-ray diffraction (XRD) technique and ab initio calculations, we reveal that the face-center-cubic (fcc) phase, rather than the hexagonal-close-packed (hcp) phase, is thermodynamically stable in the Mo CrFeCoNi HEA system under atmospheric conditions. However, a fcc to hcp transformation was identified under pressure, resulting from a pressure-induced electronic redistribution. Remarkably, the valence electron concentration has been further demonstrated as a critical factor for regulating this transformation, the reduction of which by Mo doping can encourage the hcp transformation. Our studies provide new insights into the physical processes underlying the allotropic transformation that enables customized alloy design of high-performance HEAs. Understanding pressure-related structural transitions, which can be utilized to tune the functional and mechanical properties of materials, is of great interest in materials science. Recently, the discovery of high-entropy alloys (HEAs) has opened a new era in the development of high-performance metallic materials. However, the underlying mechanisms controlling the pressure-related phase transitions in HEAs remain poorly understood. By leveraging a combination of experimental and theoretical methods, we reveal that the fcc phase is intrinsically stable for the CrFeCoNi alloy under atmospheric conditions. Interestingly, a fcc to hcp transition was identified under pressures at room temperature, due to a pressure-induced electronic redistribution. More excitingly, Mo doping has been proven to encourage the hcp transition under pressure in Mo CrFeCoNi (x = 0, 0.11, and 0.23). This fundamental understanding can facilitate a customized alloy design of high-performance HEAs by high-pressure methods. Both experimental and theoretical methods reveal the fcc phase, relative to the hcp phase, is thermodynamically stable for the prototypical CrFeCoNi multicomponent alloy under atmospheric conditions. However, a fcc to hcp transformation was identified under pressure, resulting from a pressure-induced electronic redistribution. Furthermore, Mo doping has been proven to encourage hcp transformation under pressure in a Mo CrFeCoNi (x = 0, 0.11, and 0.23) alloy system.