Aging and deaging effects in shape memory alloys

Physical properties in shape memory alloys are known to change as a result of aging over time. However, undesired aging effects in the martensite phase can be eliminated once the aged martensite is brought into the parent phase, often referred to as deaging. We propose a Landau free-energy model to study the aging and deaging of martensite. These two effects can be modeled via the increase and decrease of an internal field which adopts the same "symmetry" as the crystal symmetry of the host lattice. Time-dependent simulations based on our model successfully reproduce many of the observed martensite aging effects, such as martensite stabilization, rubberlike behavior, the domain memory effect, and aging of the elastic modulus, as well as deaging effects in the parent phase, including elimination of martensite aging and parent phase stabilization. Furthermore, we predict the time-dependent change of the elastic modulus and the stress-strain response in the parent phase, which need to be verified experimentally.