The mechanical behaviour of some titanium trialuminide intermetallics prepared using mechanical milling techniques

Titanium trialuminides have interesting strengths at high temperatures and may become useful engineering materials providing their toughnesses can be improved. One possible way to achieve this is by structural refinement. In the present study, powders of two titanium trialuminide alloys with L12 crystal structures have been milled to refine their microstructure and then consolidated by hot isostatic pressing. The behaviour of the powders during milling has been examined, and the mechanical properties of the consolidated materials evaluated and compared with the properties of bulk materials. During milling the microstructure was refined to about the micrometre level, but there were no signs of significant disordering or other changes of crystalline structure as often found during intense ball milling. Following consolidation, the materials retained significant work hardening but, despite their refined microstructures, were somewhat more brittle than the reference states. The materials with fine grain sizes failed by intergranular failure rather than by transgranular cleavage as seen for materials of larger grain size. The fracture behaviour is discussed in terms of the failure mechanisms in titanium trialuminides.