Effects of Al2O3 and Cr2O3 on the microstructure and properties of Mo alloys prepared via vacuum sintering

Abstract

The dilemma of strength and ductility of Mo alloy at ultra-high temperature (above 1300 °C) limits its application in space reactors and other high-temperature environments. Single oxide enhancement has been unable to meet these use requirements. In this research, a strategy of synergistic reinforcement of Mo alloys with nanosized Al2O3 and Cr2O3 ceramic particles was proposed. A 300−400 nm Mo alloy powder was prepared by liquid‒solid doping, and in situ self-generated nanosized oxides were obtained. The grain size of vacuum sintered Mo alloy was very fine, at only 5.3 μm, which was one tenth of the particle size of commercial Mo alloy. Al2O3 and Cr2O3 particles were distributed in the grains of the Mo matrix, which effectively prevented the growth of Mo grains during vacuum sintering and reinforced the Mo alloy. The maximum flow stress of the Mo–Al2O3–Cr2O3 alloy reached 367 MPa at 1000 °C/1 s−1, which was better than that of the single-oxide reinforcement. The ultimate tensile strength (UTS) of the Mo–Al2O3–Cr2O3 alloy was 862 MPa, which was twice that of pure Mo. The preparation process is simple and available for industrial production. Synergistic strengthening of multiple oxides will be the best strategy for strengthening refractory alloys in the future.