Quantitative evaluation of microstructure in mo-si-b-tic alloy produced by melting and tilt casting methods

Abstract

Mo-Si-B-TiC alloys are expected to be a candidate for an ultrahigh-temperature material beyond Ni-base superalloys. This work quantitatively investigated the microstructure of a Mo-Si-B-TiC alloy with the composition of Mo-5Si-10B-10TiC (65Mo alloy) (at%) produced via arc-melting and tilt-casting techniques. The alloy was composed of four constituent phases: Mo solid solution (Moss), Mo5SiB2(T2), (Ti, Mo)Cx, (Mo, Ti)2C, and their eutectic (or peritecteutectic) phases. The compositions of the constituent phases were determined by electron beam micro analyzer (EPMA). Scanning electron microscopy - backscattered electron diffraction (SEM-EBSD) measurements revealed that T2 and (Ti, Mo)Cx phases have orientation relationships with Mo phase: {110}Mo//(001)T2, Mo//T2 and {110}Mo//{111}(Ti,Mo)Cx, Mo//001(Ti,Mo)Cx. Furthermore, the three-dimensional SEM observation with the combination of the focused ion beam (FIB) serial sectioning technique demonstrated that the T2 phase had a thin plate shape with the orientation of (001) as plate surfaces and of {100} as side ones.