Effect of Al/Ti ratio on the microstructure, texture and incipient plasticity of (CoNiCr0.5)95AlxTiy high entropy alloys

Abstract

To analyze the incipient plasticity and then optimize the micromechanical behavior of HEAs, the FCC (CoNiCr0.5)95AlxTiy (x = 1, 3, 4 and y = 4, 2,1 (at.%)) HEAs were selected and thermomechanical processed, and corresponding microstructure, mechanical property and incipient plasticity were investigated and discussed. As the Al/Ti ratio changes from 1/4 to 4/1, the average GND of HEAs decreases from 1.11 × 1014 m−2 to 1.05 × 1014 m−2, and the contents of the A {110} <111> and CopperTwin {552} <115> reach to 11% and 4.4%, respectively. Meanwhile, the ductility of HEA increases from 10.6% to 13.9% with the increased Al/Ti ratio, while the strength decreases from 1221.1 MPa to 910.3 MPa. Nanoindentation results show that the normalized maximum stress τmax/μ of the HEAs exhibit the value of (1/18–1/12)μ, and the average activation volume v∗are calculated to be 3.2–3.4 Ω. These indicate that the incipient plasticity of (CoNiCr0.5)95AlxTiy possesses heterogeneous dislocation nucleation triggered by cooperative migration of multiple atoms via vacancies.