Quantitative evaluation of microstructure in Mo-Si-B-TiC alloy produced by melting and tilt casting method

Abstract

Mo-Si-B-TiC alloys are expected to be a candidate for an ultrahigh-temperature material beyond Ni-base superalloys. This work quanti- tatively 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 (Mo ss ), Mo 5 SiB 2 (T 2 ), (Ti, Mo)C x , (Mo, Ti) 2 C, and their eutectic (or peritecteutectic) phases. The compositions of the constituent phases were determined by elec- tron beam micro analyzer (EPMA). Scanning electron microscopy – backscattered electron diffraction (SEM-EBSD) measurements revealed that T 2 and (Ti, Mo)C x phases have orientation relationships with Mo phase: { 1¯10 } Mo // (001) T2 , < 111 > Mo //< 001 > T2 and { 1¯10 } Mo // { 1¯11 } (Ti , Mo)Cx , < 111 > 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 T 2 phase had a thin plate shape with the orientation of (001) as plate surfaces and of { 100 } as side ones. [doi:10.2320 / matertrans.M2017194]