The as-cast AlxCrTaTi refractory medium entropy alloys with good room-temperature mechanical properties and high-temperature oxidation resistance

Abstract

Refractory medium entropy alloys (RMEAs) usually show good mechanical properties at high temperature. Unfortunately, their very poor room-temperature plasticity and high-temperature oxidation resistance still greatly limit their practical application. In this work, the room-temperature mechanical properties and high-temperature oxidation resistance of AlxCrTaTi RMEAs (x = 0, 0.15, 0.25, 0.35) are systematically studied. It is found that the AlxCrTaTi RMEAs exhibit very high yield strength of about 1700 MPa and plasticity of above 10%. For Al-bearing RMEAs, a composite oxide layer containing Al2O3 is formed on the alloy surface. Under the synergistic effect with the CrTaO4 oxide layer in the middle layer, Al0.25CrTaTi alloy possesses good oxidation resistance at 1000 ℃ for 100 h with the oxidation weight gain of only 7.3 mg/cm2.