TITANIUM ALUMINIDES FROM COLD-EXTRUDED ELEMENTAL POWDERS WITH AL-CONTENTS OF 25-75 AT-PERCENT AL

Titanium aluminide alloys were prepared from cold-extruded elemental T i and Al powders with compositions ranging from 25 to 75 at % Al. The production route in this study includes four essential steps: mixing, precompaction, cold-extrusion and reaction treatment. During reaction treatment, the intermetallic phases Ti3Al, TiAl and TiAl3 are formed b y interdiffusion of Ti and Al, and pore formation takes place because of the different diffusivities of Ti and Al, The processes of phase fo rmation, as well as pore formation, were studied by means of calorimet ric, dilatometric and metallographic methods. In order to obtain nearl y fully dense specimens, the technique of hot isostatic pressing was a pplied. The sintering behaviour and microstructures of the prepared al loys are reported.