SOLIDIFICATION BEHAVIOR AND MICROSTRUCTURE EVOLUTION OF Si BEARING TiAl ALLOY

The solidification behavior of Ti 52 Al 48 x Si ( x =0, 0 5, 1 0, 2 0, 3 0, 6 0, mole fraction, %) alloys prepared by ingot metallurgy, has been studied with differential thermal analysis (DTA) and microstructure examination. Two kinds of Ti 5Si 3 phase were found in Ti 52 Al 48 x Si ( x =0 5, 1 0, 2 0) alloys. The first one was formed during L →Ti 5Si 3+ L 1, and the second one was characteristic of whiskers in eutectic morphology formed during L 2→α+Ti 5Si 3. The third kind of Ti 5Si 3 phase was formed in Ti 52 Al 48 3Si alloy by a eutectoid reaction of α→γ +Ti 5Si 3. With addition of Si up to 6 0 %, the solidification path was completely different from the other alloys.