Evolution of microstructure and mechanical properties of Ti/TiB metal-matrix composite during isothermal multiaxial forging

Mechanical behavior and microstructure evolution of a Ti/TiB metal-matrix composite during multiaxial forging (MAF) at 700 and 850 degrees C and a strain rate 10(-3) s(-1) were studied. The composite was produced via in-situ 3Ti + TiB2 -> 2Ti+2TiB reaction during spark plasma sintering at 1000 degrees C. Mechanical behavior in terms of aggregated sigma-Sigma epsilon curves during MAF at both temperatures demonstrated a pronounced softening following by a steady-like flow stage. Microstructure evolution during MAF at both temperatures was associated with (i) dynamic recrystallization of the titanium matrix and the formation of dislocation-free areas of similar to 1 mu m in diameter and (ii) shortening of TiB whiskers by a factor of similar to 3. MAF at 700 and 850 degrees C to cumulative strain similar to 5.2 resulted in a considerable increase in the low-temperature ductility without substantial loss in strength. Contributions of different strengthening mechanisms into the overall strength of the Ti/TiB metal-matrix composite were discussed. (C) 2018 Elsevier B.V. All rights reserved.