Influence of molybdenum content on the microstructure of spark plasma sintered titanium alloys

Five titanium-based alloys containing ۴, ۸, ۱۲, ۱۶, and ۲۰ wt% molybdenum additive were fabricated by spark plasma sintering process at ۱۲۰۰ °C. The samples were scrutinized in terms of relative density, phase evolution, and microstructural development. The relative density reached ۹۹.۹% with the molybdenum addition up to ۱۶ wt% but slightly dropped in the sample with ۲۰ wt% additive. In the specimens with ۴ wt% Mo, molybdenum solved completely in the matrix and three different phase morphologies were observed, namely continuous α-Ti, laminar α-Ti, and very thin laminar β-Ti. With increasing Mo content to ۲۰ wt%, widespread single β-Ti appeared alongside remained Mo and α-Ti. Ductile fracture mode was dominant in the samples with low Mo contents whilst it changed to brittle in the specimens with higher content of molybdenum.