Short range order and phase separation in Ti–Al alloys

The phase decomposition mechanism operating in binary Ti–Al alloys in the two phase α+α2 region has been investigated. A Ti–15at.%Al alloy was aged in the range 450–750°C for various time periods. The resulting microstructures were studied by transmission electron microscopy (TEM) and atom probe field ion microscopy (APFIM). Computer simulations of phase separation in this alloy were also carried out using a dynamic Ising model. Results from the computer simulations suggest decomposition occurs via a conditional spinodal route, whereby compositional phase separation is contingent upon prior ordering of the matrix. Experimental studies to date are fully consistent with this mechanism.