Molecular Dynamics Simulation Of Interface Migration Of Twinned Martensite In CU-AL-NI Shape Memory Alloy

Martensitic transformation (MT) has been widely applied in many modern industrial fields. One of its major applications is the shape memory effect. The shape memory effect of Cu-Al-Ni alloy in this study is caused by the martensitic transformation and the reverse transformation. During the transformation there is a basic physical process that the interface,including the habit plane between phases and the twin plane between variants,migrate under the internal and external chemical and mechanical driving forces.The current study is based on the research of dynamics of interface propagation in MT. The molecular dynamics approach is applied to simulate the dynamics of phase transformations in Cu-Al-Ni shape memory alloy. It is our aim to make it more clear the atom migration on the twin interface under thermo and mechanical driving forces.Basics of MT and molecular dynamics simulation are given as the introduction. After that, we develop the original modified embedded atom method (MEAM) on the screening function and a pair potential for some complicated reference structures. MEAM potentials with consideration of second nearest neighbor effect are then developed for Cu-Al-Ni tenary alloy system. With these, thermo and stress-induced MT simulations for some initial configuration are conducted. We observed successfully the thermo-elastic MT and pseudo-elastic behavior in stress-induced MT, as well as the hysteresis in both martensitic phase transformations. The hysteresis is proved to be tightly associated with the growth and consumption of martensite variants in the forward and inverse MT and also the interface migration.