Stress-induced phase stabilization and transformation in equiatomic CuZr B19’ martensite: A DFT study

Abstract

The stress-induced martensitic transformation of CuZr-based alloy takes an indispensable part in its shape memory effect and plasticity improving. CuZr–B19’ phase as an unstable martensite product of CuZr–B2 austenite has been widely reported by experimental and DFT methods. However, the instability of B19’ structure ignored in theoretical calculation drives it transform into B33 phase after structural relaxation, which makes computational properties of B19’ phase untrusted. Therefore, in this work, we prevented B19’ phase from relaxation phase transition by applying external force to supply a reliable structure for its subsequent properties calculations. In addition, a reversible phase transition between phases B19’ and B33 was found and the theoretical value of transformation stress was determined. The changes of elastic modulus, formation enthalpy and electronic property of two phases (B33 and B19’) under various pressures were compared and analyzed. The results aforementioned justify that CuZr–B33 is an indirect martensite product of CuZr–B2 phase, which explains why some peoples observed B33 phase in experiments, while others did not.