Phase-field modeling of martensitic microstructure in NiTi shape memory alloys

A phase-field model is developed to study the cubic to monoclinic martensitic phase transformation in nickel–titanium (NiTi) shape memory alloys. Three-dimensional phase-field simulations show the nucleation and growth of monoclinic B19′ multivariants that form a polytwinned martensitic microstructure. Parametric studies demonstrate that mechanical constraints and crystallographic orientation govern the patterning of martensitic twin variants in the formation of strain-accommodating microstructures. Pairing of twin variants is studied by comparing the phase-field simulation results with the crystallographic solutions of compatible twins. The phase-field method developed in this work is generally applicable to simulate the dynamic microstructure evolution of metals and alloys that produce low-symmetry phases through martensitic transformation.