Phase change and mechanical behaviors of Ti_xCoCrFeNiCu _1-yAl_y high entropy alloys

The alloying effects of the Al, Ti, Cu, and Co in a typical Ti _xCoCrFeNiCu_1-yAl_y high entropy alloy (HEA) were systematically studied. The phase change of the HEAs is closely related to the atomic packing efficiency of the phases. The high entropy of the alloy will largely lower the Gibbs free energy when the enthalpy of the alloys are not changed too much, and the high entropy phase can be an equilibrium stable one. The HEAs can have ultrahigh fracture strength at room temperature and high temperature, e.g., yield strength of 1400 MPa at 500°C.