DOES A DISORDERED GAMMA-TIAL PHASE EXIST IN MECHANICALLY ALLOYED TI-AL POWDERS

An fcc phase has been reported to form in mechanically alloyed titaniu m-aluminum alloys. This fcc phase forms after an amorphous phase durin g milling and has been found to be stable up to very high temperatures . Different investigators have interpreted the formation of this fcc p hase as (i) a product of crystallization of the amorphous phase, (ii) a supersaturated solid solution of titanium in aluminum, (iii) the dis ordered form of the gamma-TiAl phase, or (iv) a contaminant phase. The present paper analyzes the available results and concludes that this is a contaminant phase, most probably TiN.