摘要
A Ti-48Al (at. pet) alloy prepared by elemental powder metallurgy (EPM) has been heat treated under various conditions. Through optical and scanning electronic microscopy, EDAX, XRD analysis, and DTA, it was shown that the hot pressed microstructure consisted of alpha(2)-Ti3Al and TiAl phases. The alpha(2)-Ti3Al phase was island-like, and had a high stability and heredity in subsequent heat treatments. The supersaturation of Al in the island-like alpha-Ti3Al phase strongly influenced the transformation of alpha(or alpha(2)) to alpha(2)/gamma lamellar colonies. After a heat treatment at 1380 degrees C for 0.5 h and 1000 degrees C for 8 h, a fully lamellar microstructure with a colony size of 50 mu m was obtained. This result indicates that a homogeneous composition and an equilibrium microstructure in EPM TiAl-base alloys can only be obtained after heat treatment at temperatures above alpha transus temperature (T-alpha).
A Ti-48Al (at. pet) alloy prepared by elemental powder metallurgy (EPM) has been heat treated under various conditions. Through optical and scanning electronic microscopy, EDAX, XRD analysis, and DTA, it was shown that the hot pressed microstructure consisted of alpha(2)-Ti3Al and TiAl phases. The alpha(2)-Ti3Al phase was island-like, and had a high stability and heredity in subsequent heat treatments. The supersaturation of Al in the island-like alpha-Ti3Al phase strongly influenced the transformation of alpha(or alpha(2)) to alpha(2)/gamma lamellar colonies. After a heat treatment at 1380 degrees C for 0.5 h and 1000 degrees C for 8 h, a fully lamellar microstructure with a colony size of 50 mu m was obtained. This result indicates that a homogeneous composition and an equilibrium microstructure in EPM TiAl-base alloys can only be obtained after heat treatment at temperatures above alpha transus temperature (T-alpha).
