Evolution of microstructure and mechanical properties of Ti-based metal-matrix composites during hot deformation

Abstract

Two Ti-based composites, viz. Ti/TiB and Ti-15Mo/TiB were produced by spark plasma sintering using a Ti-10wt.%TiB2 powder mixture at 1000°C or Ti-14.25(wt.)%Mo-5(wt.)%TiB2 powder mixture at 1400°C, respectively. Specimens of the metal-matrix composites (MMCs) were subjected to uniaxial compression in the temperature range from 500 to 1050°С to determine processing window. Processing maps for both MMCs were constructed and analyzed. Mechanical behavior and microstructure evolution of both MMCs during multiaxial forging (MAF) at 700°C and at a strain rate 10-3 s-1 were studied. The flow stress for the Ti-15Mo/TiB MMC during MAF was ∼2 times higher than that for the Ti/TiB composite. Microstructure evolution during MAF of Ti/TiB MMC was associated with continuous dynamic recrystallization of the titanium matrix and shortening of TiB whiskers by a factor of ~3. The Ti-15Mo/TiB composite microstructure after did not demonstrate the development of recrystallization.