Plastic TiZrHfCoNiCu high entropy alloy via stable B2 phase

Abstract

(Ti, Zr, Hf)(Co, Ni, Cu) high entropy alloys (HEAs) have excellent properties such as high-temperature shape memory property and high yield strength that have attracted widespread attention in recent years, but their application has been limited due to the lack of plastic deformability. In this work, we examined the possibility of synthesizing a new HEA with good mechanical properties by controlling the formation ability of metastable amorphous (am) and B2 phases for Ti16.5Zr17Hf16.5Co16.5Ni16.5Cu17 HEA. The as-spun amorphous and [am＋B2] phase ribbons with good bending plasticity were formed. The mixed-phase ribbon exhibits higher tensile plasticity than the amorphous ribbon because of the easy generation of shear bands and the suppression of their propagation around the B2 phase. Besides, the B2 phase is formed for the cast rod with a diameter of 2 mm. The B2 rod exhibits compressive strength up to 2254 MPa and a plastic strain of about 5%. The B2 alloy rod also has high thermal stability and keeps good mechanical properties after annealing under 973 K for 1.8 ks. The high mechanical strength and good plasticity of the B2 HEA are due to the generations of deformation-induced dislocation and martensite B33 phase. The synthesis of the B2 HEA with excellent mechanical properties through the deformation-induced martensite transformation is promising for future structural material.