Phase, microstructure and mechanical properties evaluation of AlCoCrFeNi high-entropy alloy during mechanical ball milling

Abstract

The phase transition, microstructure evaluation and mechanical properties of AlCoCrFeNi alloy during mechanical ball milling were studied. The results show that the content of FCC phase decreases gradually with increasing milling time to 20 h. The amorphous phase can be obtained completely when extending the milling time to 84 h. The phase composition of the sintered AlCoCrFeNi alloy exhibits the trend opposite to that of the alloy powder after ball milling. An alternating BCC/FCC lamellar morphology consisting of uniformly distributed B2 particles was obtained after the hot-pressed sintering of the milled AlCoCrFeNi powder. The alloy with amorphous precursor exhibits high ultimate strength of 1947 MPa, about 74.8 % higher than that of the alloy without milling. This excellent mechanical property could be ascribed to its alternating BCC/FCC heterogeneous structure, which contains coherent interfaces with an orientation relationship of 11¯0BCC//11¯0B2and110BCC//110B2, semi-coherent interfaces between B2 and FCC phases, and incoherent interfaces between FCC and BCC phases.