Compression deformation of single-crystal Pt₃Al with the Ll ₂ structure

The plastic deformation behaviour of single crystals of Pt₃Al with a chemical composition of Pt-27 at.%Al was investigated in compression from 77K to 1,273K. The Ll₂ structure is not stable below around 220 K, transforming into either D0c, D0c' or Pt₃Ga structures. {001} slip system was operative for most loading axis orientations while {111} slip system was operative for a narrow orientation region close to [001]. The CRSS for {111} slip gradually decreases in the temperature range where the Ll₂ structure is stable, followed by a sharp decrease above 1,073 K, without showing positive temperature dependence. On the other hand, the CRSS for {001} slip gradually decreases below 673 K and moderately increases above 673 K. Dislocations on {111} tend to align along their screw orientation, suggesting high Peierls stress for their motion, while those on {001} are edge-oriented and fairly curved on a local scale, suggesting relatively low Peierls stress. Dislocations on both {111} and {001} with a Burgers vector b = [101] dissociate into two collinear superpartials with b = 1/2[101] separated by an anti-phase boundary.