Deformation behavior and microstructure evolution of a Ti/TiB metal-matrix composite during high-temperature compression tests

Publication date: 15 December 2016
Source:Materials & Design, Volume 112
Author(s): M. Ozerov, M. Klimova, A. Kolesnikov, N. Stepanov, S. Zherebtsov
A Ti/TiB metal-matrix composite (MMC) was produced by spark plasma sintering (SPS) using a Ti-10wt.%TiB2 powder mixture at temperatures of 850 or 1000°C, corresponding to the α or β phase fields of Ti, respectively. The structures of both conditions were similar; however, a higher fraction of unreacted TiB2 and finer TiB whiskers were observed after sintering at 850°C. The mechanical behavior and microstructural response of the MMC to uniaxial compression in the temperature range from 500 to 1050°С was studied. At low temperatures of 500–700°C, the MMC sintered at 1000°C had a greater strength and lower ductility. At higher temperatures of 850–1050°C, the MMC sintered at 1000°C was compressed to a 70% strain without cracking, whereas surface cracks were observed in the specimen sintered at 850°C. Microstructure evolution of the Ti matrix was associated with the i) formation of a cell microstructure at 500°C, ii) continuous dynamic recrystallization at 700°C, and iii) discontinuous dynamic recrystallization at temperatures ≥850°C. A considerable decreasing the length of the TiB whiskers, which occurred much slower in the β phase, was observed during deformation. The mechanisms governing the mechanical behavior in different temperature regions were established using activation energy analysis.

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