Abstract:The morphology of discontinuous coarsening in Ti-48Al-2Cr(mole fraction, %) was investigated. Three types of morphology were observed in TiAl specimens heat-treated at temperatures ranging from 950℃to 1250℃. TypeⅠhas straight coarsened secondary lamellae nearly parallel to the colony boundary, and it forms along the colony boundaries nearly normal to the primary lamellae. Type-Ⅱhas straight coarsened secondary lamellae nearly normal to the colony boundary. Type-Ⅲconsists of curved secondary lamellae that have no distinct orientation with the colony boundary and the primary lamellae. At the same time, the effect of temperature and the orientation between the lamellae and the colony boundaries on the morphology was analyzed.

Key words: TiAl based alloy;discontinuous coarsening;morphology