Nickel aluminum shape memory alloys via molecular dynamics

Morrison, Keith R. M.S.M.S.E., Purdue University, August 2014. Nickel Aluminum Shape Memory Alloys via Molecular Dynamics. Major Professor: Alejandro Strachan. Shape memory materials are an important class of active materials with a wide range of applications in the aerospace, biomedical, and automobile industries. These materials exhibit the two unique properties of shape memory and superelasticity. Shape memory is the ability to recover its original shape by applying heat after undergoing large deformations. Superelasticity is the ability to undergo large, reversible deformations (up to 10%) that revert back when the load is removed. These special properties originate from a reversible, diffusionless solid-solid phase transformation that occurs between a high temperature austenite phase and a low temperature martensite phase. The development of the martensite microstructure is not well understood; this is especially true in regards to the role of size and mechanical constraints that dominate the properties in nanoscale samples. The goals of this research are to use molecular dynamics (MD) to (1) study the effects of simulation size on the martensite transformation to determine the ultimate limit of miniaturization, (2) to investigate the effects of mechanical constraints on the martensite transformation and resulting microstructure, and (3) to explore the effects of grain size in