Microstructure and Mechanical Properties of Sintered TiAl

Abstract

Pulverised TiAl powder was cold isostatically pressed at 392 MPa and the resulting compact sintered at temperatures up to 1623 K to produce sintered TiAl with relative densities as high as 91%. This process formed a laminated structure consisting of TiAl and Ti3AI, which gave a high compressive yield strength accompanied by embrittlement of the sintered TiAl compacts, no bending plastic deformation being observed at room temperature. When centrifugally atomised powder melted in a CaO crucible was used, sintered TiAl specimens, apparently of full theoretical density, could be obtained by canned hipping at 1473 K under a pressure of 98 MPa. The hipped TiAl specimens had a grain size of ~20–30 μm, and grain coarsening was not observed, even when specimens were annealed for 720 ks at temperatures of 1273–1373 K. Hipped specimens annealed at 1273 K had a yield strength of 388 MN m ⁻² at room temperature, and bending ductilities > 0·4% were obtained. PM/0426