Computer simulation of microstructural evolution in Ni-rich TiNi shape memory alloys under applied stresses

Coherent Ti₁₁Ni₁₄ precipitation in TiNi shape memory alloys and its variation under applied stresses were investigated using a diffuse-interface phase-field model. In this model, the structural difference between the precipitate phase and the matrix as well as the orientational difference between precipitate variants are distinguished by structural field variables, whereas the compositional difference between the precipitate phase and the matrix is distinguished by a concentration field variable. The temporal variation of the field variables is determined by solving the Ginzburg-Landau equations and the Cahn-Hilliard equation. Precipitate morphologies and their variation under strain-constraints were studied.