What Determines the Martensitic Transition Temperature in Alloys ?

Abstract
The intriguing puzzle is addressed concerning the dramatic dependence generally observed of the Martensitic transition temperature on the composition of alloys. Based on one of the simplest possible systems, the Ti_cZr_1-c alloy system, a theory is developed including the effect of a disorder scattering of the phonons due to a mass difference between the elements. The depression of the Martensitic transition temperature, ΔMs, is shown to depend parabolically on concentration c, as c(1-c), for small depressions. For larger ΔMs an enhancement at intermediate c is predicted. This gives rise to a more triangular dependence as a function of c. The theory contains only one phenomenological parameter. Comments are given relevant for other more complicated alloy systems.