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

Abstract

Mechanical behavior and microstructure evolution of a Ti/TiB metal-matrix composite during multiaxial forging (MAF) at 700 and 850 °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 °C. Mechanical behavior in terms of aggregated σ-Σε 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 ∼1 μm in diameter and (ii) shortening of TiB whiskers by a factor of ∼3. MAF at 700 and 850 °C to cumulative strain ∼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.