Mechanism for metastable phase formation in undercooled Ti-Al peritectic alloys

Melt undercooling technique has been proved to be a powerful tool to investigate the formation of metastable phase in rapid solidification processing. Here, the recently observed phase evolution behaviour of the near equal atomic percent Ti-Al alloys was analyzed, as a function of melt undercooling, by thermodynamic and kinetic calculation. It was found that the formation of metastable phase is lightly predicted by the chemical Gibbs energy difference among competing phase but strongly controlled by kinetic effects arising from the competition of nucleation. The transient nucleation theory, with a consideration of incubation time, was proved to be an effective tool to explain the metastable phase formation in the undercooled near equal atomic percent Ti-Al alloys. (C) 2003 Elsevier B.V All rights reserved.