Phase equilibria and microstructure evolution of Al–Mo–Ti ternary alloys

Phase equilibria in Ti-lean part of the Al–Mo–Ti ternary system is investigated to understand the microstructure evolution of near-equi-atomic MoAl alloys containing Ti up to 17 at.%. A partial reaction scheme is proposed based on experimental study. A high temperature ternary A2(bcc)-β phase with Ti concentrations ranging from 13 to 17 at.% decomposes into A15 Mo3Al–D022 Al3Ti two-phase lamellar structure in a manner similar with a eutectoid reaction through a continuous cooling. The decomposition kinetics of the high temperature A2 phase is suppressed by adding Ti. Fine equi-axed two-phase structure is also obtained by an isothermal aging of a retained high temperature A2 phase.