Thermodynamics of the martensitic transformation in CuZn alloys

It is supposed that the correspondence relationship between atoms of the new and parent phases as shown in Bain mechanism exists in the martensitic transformation of CuZn alloys. Applying the known values of thermodynamic properties and treating the ordering problem of CuZn alloys by means of the BWG model, a general formula for the driving force ΔG^{β′→α′} of the phase transformation is derived. This formula is used to calculate the equilibrium temperature T₀ and the starting temperature M_s of the martensitic transformation in CuZn alloys. The calculated M_s values are in very good agreement with the experimental ones. Calculations also indicate that the degree of ordering of the parent phase has a tremendous influence upon the values of M_s in CuZn alloys.