PLASTIC-DEFORMATION OF CHROMIUM-MODIFIED LL2AL3TI .1. FLOW BEHAVIOR

The flow behaviour of single-crystal L1(2) Al67Cr8Ti25 was measured as a function of orientation and temperature between 77 and 1250 K. Thes e results were then correlated with an analysis of the operating slip systems using the two-surface slip trace technique, stabilities and en ergies of various stacking faults based on gamma surface calculations using N-body potentials, and weak-beam transmission electron microscop y studies of dislocation structures (presented in the accompanying pap er). The flow behaviour of the material is found to correlate closely with the nature of the dissociation of the [110]{111} superdislocation s carrying the plastic deformation. At low temperatures the plasticity is carried by 1/3[112] superpartial dislocations separated by superla ttice intrinsic stacking faults, which have nonplanar cores, and there fore the flow stress shows a rapid decrease with increasing temperatur e at low temperatures. At high temperatures the plasticity is carried by antiphase-boundary dissociated 1/2[110] superpartials which have pl anar cores and therefore the critical resolved shear stress is tempera ture indepdendent in this temperature range.