STRENGTHENING MECHANISMS IN CUBIC TITANIUM TRIALUMINIDE ALLOYS

Titanium trialuminide alloys stabilised to the cubic crystal structure show strength variations with temperature that vary from one alloy to another. For some alloys significant strength increases are seen at low temperatures, while for other alloys such strengthening may occur at high temperatures. These strength increases are not explained by dislocation core structures or cross-slip processes but by solute effects or by fine Al2Ti precipitate particles present in the material or formed during testing. Analysis of dislocation mobility at low temperatures by measurements of activation volume suggests that mobility at very low temperatures is controlled by a mechanism of unblocking and blocking of dislocation segments through Peierls valleys, probably influenced by solute additions.