Dislocation Interactions in Two-Phase TiAl Alloys

Abstract

Dislocation configurations produced by room and high temperature deformation of two alloys with compositions Ti-48A1 and Ti-47.5Al-2.5Cr have been compared. At room temperature the major differences between the two alloys is the increased twinning activity and that of 1/2 <112] superdislocations in the chromium containing alloy while the binary alloy contains a larger contribution from <101] superdislocations. At 400°C, the temperature at which a peak in flow stress is observed in both alloys, an increase in twinning activity and emission of 1/2<110] dislocations on (001) planes is observed from twin intersections in both materials. The contribution of superdislocations to the deformation process is limited and their effect on the flow stress increase appears irrelevant. Instead the anomalous strengthening effect has been related to the cross-slip of single dislocations from cube planes, on which they are emitted, to octahedral planes where they can also glide.