PLASTIC-DEFORMATION OF AN IRON-MODIFIED TITANIUM TRIALUMINIDE ALLOY

Mechanical properties and dislocation structures have been studied from room temperature to 700-degrees-C in a titanium trialuminide alloy modified to the composition Al5Ti2Fe. In compression the material shows extensive ductility with the yield stress increasing above 300-400-degrees-C, but in bend testing it is very brittle. At low temperatures undissociated <110> dislocations are mobile and deformation is controlled by Peierls effects and by extensive work hardening. At intermediate temperatures many dislocations dissociate into mobile superdislocations giving rise to serrations in the stress-strain curve; undissociated segments appear immobile because of a solute-associated core relaxation. At high temperatures dislocations are dissociated as superdislocations, mobile on both octahedral and cube planes, with cross slip between these planes bringing about high temperature strengthening. The low ductility in bend testing may be related to the high work hardening as well as the intrinsic cleavage weakness of the material.