High toughness and strength of Mo-12Si-8.5B-ZrB2 alloy resulting from a bimodal α-Mo grain structure

Abstract

Designing a bimodal α-Mo grain structure in Mo-12Si-8.5B-ZrB2 alloy was achieved via mechanical alloying followed by hot pressing. This bimodal structure consisted of a major of nano-scaled α-Mo grains and partial micron-scaled α-Mo grains. The effective cooperation of these fine and coarse α-Mo in the Mo-12Si-8.5B-ZrB2 alloy was very beneficial for improving its toughness as well as strength. The high toughness was mainly attributed to the in-situ toughening and crack trapping effects originating from the coarse α-Mo. While the high strength was owing much to the grain boundary strengthening of the fine α-Mo. When the volume fraction ratio of the fine and coarse α-Mo grains was approximately 6:1, the fracture toughness value reached 13.1 MPa·m1/2 in the bimodal alloy, showing a 18% increase compared to an ultrafine-grained alloy. Simultaneously, a high compressive strength with 2998 MPa was also maintained.