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

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 degrees C, corresponding to the a or beta 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 degrees C. The mechanical behavior and microstructural response of the MMC to uniaxial compression in the temperature range from 500 to 1050 degrees. was studied. At low temperatures of 500-700 degrees C, the MMC sintered at 1000 degrees C had a greater strength and lower ductility. At higher temperatures of 850-1050 degrees C, theMMC sintered at 1000 degrees C was compressed to a 70% strain without cracking, whereas surface cracks were observed in the specimen sintered at 850 degrees C. Microstructure evolution of the Ti matrix was associated with the i) formation of a cell microstructure at 500 degrees C, ii) continuous dynamic recrystallization at 700 degrees C, and iii) discontinuous dynamic recrystallization at temperatures >= 850 degrees C. A considerable decreasing the length of the TiB whiskers, which occurred much slower in the beta phase, was observed during deformation. The mechanisms governing the mechanical behavior in different temperature regions were established using activation energy analysis. (C) 2016 Elsevier Ltd. All rights reserved.