THERMODYNAMICS OF THE MARTENSITIC-TRANSFORMATION IN CU-AL ALLOYS

The phase diagram of Cu-Al system has been fully utilized to derive several thermodynamic parameters of Cu-Al alloys on the basis of the regular solution model. A statistical method has also been used to deal with alpha --> alpha' and beta --> beta' ordering transitions accompanying the martensitic transformation in Cu-Al alloys. The equilibrium temperatures T0* and T0, as well as M(s) temperature have then been calculated theoretically in Cu-Al alloys with various compositions, and the M(s) obtained are in good agreement with the experimental ones. The calculated results also show that the equilibrium temperature of the ordered alpha' and beta' phases, T0, is higher than that of the disordered alpha and beta-phases, T0*.