Age Hardening of AlCrMoNiTi High Entropy Alloy Prepared by Powder Metallurgy

The AlCrMoNiTi high entropy alloy was prepared by powder metallurgy process. Its microstructure and hardness of as-cast and annealed state were studied. The results show that the as-cast alloy exhibits a mixture of the dendrite (Cr, Mo)-rich bcc phase and the interdendrite (Al, Ni, Ti)-rich fcc phase. The aged alloy can obtain a peak hardness HV of 6150 MPa at 900 °C, and then anneal softening occurs at 1000 °C, but its hardness HV still maintained at a high level of 5160 MPa. This shows that the AlCrMoNiTi alloy exhibits a good high-temperature age hardening performance. Age hardening of the alloy is mainly attributed to the grain refinement strengthening at 800 °C and the precipitation hardening of the second phase (bcc2) at 900 °C. The disappeared second phase and grain coarsening are the main reasons for the softening anneal at 1000 °C.