SOLID-STATE HOT-PRESSING OF ELEMENTAL ALUMINUM AND TITANIUM POWDERS TO FORM TIAL (GAMMA+ALPHA(2)) INTERMETALLIC MICROSTRUCTURE

The elemental powder metallurgy (EPM) process is used to prepare TiAl- base intermetallics. An EPM process conducted by two-stage solid-state hot pressing was employed to prepare TiAl-base intermetallics and to investigate the resulting microstructural changes. The results showed that the TiAl3 phase forms in the first stage. During the temperature increase to the second sintering stage, lamellar phases start to preci pitate in the TiAl3 matrix. Further, the TiAl3 phase transforms to TiA l, and Ti3Al layers develop in the remaining titanium particles. Meanw hile, the lamellar phases grow into ring-type structures between the T iAl matrix and the Ti3Al layers. After the second stage, the remaining titanium particles are fully reacted, and a microstructure of Ti3Al p hases enclosed by fine-grained lamellar rings in the TiAl matrix is de veloped.