ELASTIC-CONSTANTS OF BCC BINARY-ALLOYS NEAR THE A3B COMPOSITION AND THEIR RELATION TO MARTENSITIC TRANSITIONS

The present work deals with the analysis of the atomic-order dependence of the elastic constants of a BCC binary alloy near the A3B composition. The authors assume that each atom interacts with nearest and next-nearest neighbours through a pairwise interatomic potential. The configurational phase diagram of the system has been obtained from Monte Carlo simulation of a lattice model for such an alloy system. The DO3, B2 and A2 phases are found to be stable for appropriate values of the interaction parameters. The elastic constants of partially ordered configurations are calculated at T=0 K, after quenches from different temperatures Tq ranging over the stability regions of the three phases. The results are compared with experimental data corresponding to the Cu-Zn-Al shape memory alloy and their relevance in connection with the martensitic transformation is discussed.