PREPARATION OF (GAMMA-STATE HOT-PRESSING(ALPHA(2)) TYPE TIAL INTERMETALLICS FROM ELEMENTAL POWDERS BY SOLID)

A hot isostatic pressing (hipping) process is often employed to prepar e dense TiAl based intermetallics by liquid phase sintering in the ele mental powder metallurgy (EPM) field. However; hot pressing which is c heaper than hipping, not only in preparation but also in operation, is seldom used in this field since it results in the aluminium melting a nd overflowing during sintering. In the present work, the solid state hot pressing process has been developed to prepare TiAl intermetallics from elemental powders by a continuous two stage sintering cycle incl uding a solid state diffusion stage and a densification stage. The eff ect of process variables such as temperature, pressure, and time on th e density and microstructure of specimens was investigated. The result s showed that dense (alpha(2) + y) type TiAl intermetallics can be obt ained after sintering at 630 degrees C for 22 h (with the first 5 h at 45 MPa), followed by 2 h at 1250 degrees C and 45 MPa. (C) 1997 The I nstitute of Materials.