Local chemical fluctuation mediated ultra-sluggish martensitic transformation in high-entropy intermetallics

作者：Wu, Yuan; Zhang, Fei; Li, Fengshou; Yang, Yi; Zhu, Jiaming; Wu, Hong-Hui; Zhang, Yao; Qu, Ruitao; Zhang, Zhefeng; Nie, Zhihua; Ren, Yang; Wang, Yandong; Liu, Xiongjun; Wang, Hui; Lu, Zhaoping^*

来源：Materials Horizons, 2022, 9(2): 804-814.

DOI：10.1039/d1mh01612a

• SHAPE-MEMORY ALLOY
• FREE-ENERGY
• CONCENTRATION MODULATION
• SPECIMEN PREPARATION
• NONUNIFORM SYSTEM
• MICROSTRUCTURE
• STRESS
• ORDER
• NUCLEATION
• REDUCTION

Superelasticity associated with martensitic transformation has found a broad range of engineering applications, such as in low-temperature devices in the aerospace industry. Nevertheless, the narrow working temperature range and strong temperature sensitivity of the first-order phase transformation significantly hinder the usage of smart metallic components in many critical areas. Here, we scrutinized the phase transformation behavior and mechanical properties of multicomponent B2-structured intermetallic compounds. Strikingly, the (TiZrHfCuNi)(83.3)Co-16.7 high-entropy intermetallics (HEIs) show superelasticity with high critical stress over 500 MPa, high fracture strength of over 2700 MPa, and small temperature sensitivity in a wide range of temperatures over 220 K. The complex sublattice occupation in these HEIs facilitates formation of nano-scaled local chemical fluctuation and then elastic confinement, which leads to an ultra-sluggish martensitic transformation. The thermal activation of the martensitic transformation was fully suppressed while the stress activation is severely retarded with an enhanced threshold stress over a wide temperature range. Moreover, the high configurational entropy also results in a small entropy change during phase transformation, consequently giving rise to the low temperature sensitivity of the superelasticity stress. Our findings may provide a new paradigm for the development of advanced superelastic alloys, and shed new insights into understanding of martensitic transformation in general.

• 单位
  北京理工大学; 山东大学; 中国科学院; 北京科技大学