Evolution of microstructure during sintering of P/M Mo-Ti-Zr-C alloy (P/M-TZM)

A series of isothermal sintering experiments was performed at temperatures between 1250 and 22000C (2280 and 39900F) to identify the changes in microstructure which occur during sintering of a Mo-Ti-Zr-C alloy produced by powder-metallurgy techniques (P/M-TZM). Second-phase particles having a variety of compositions and morphologies were observed in the sintered billets. At temperatures below 16250C (29550F), zirconium-rich particles were observed which typically contained a dark gray central region identified as zirconium dioxide, penetrated by a light gray or gold phase identified as zirconium carbonitride containing some molybdenum. Sintering at 17500C (31800F) eliminated nearly all the zirconium carbonitride phase. Isolated titanium-rich carbonitride particles were observed after sintering at 17500C (31800F) and below. No carbonitride particles of either type were observed after sintering at 19000C (34500F) and above, but the zirconium dioxide particles persisted after sintering at all temperatures