|About this Abstract
||MS&T23: Materials Science & Technology
||Multi Scale Modeling of Microstructure Deformation in Material Processing
||Fine-tuning Superelastic Behavior of NiTi SMAs via Nanoscale Concentration Modulation Created by Ni4Ti3 Nanoprecipitate Dissolution
||Zexu Chen, Hariharan Sriram, Longsheng Feng, Yunzhi Wang
|On-Site Speaker (Planned)
NiTi shape memory alloys (SMAs) are known for their giant recoverable strains of up to ~10%. However, their strongly non-linear pseudo-elasticity can lead to strain avalanche and mechanical instability, characterized by strain plateaus and giant stress-strain hystereses. Recent studies have demonstrated that creating nanoscale concentration modulations (nanoCMs) in the B2 matrix of NiTi SMAs can precisely regulate the stress-strain behavior of the alloys because of the strong composition-dependance of the critical stress to induce the martensitic transformation. However, creating such nanoCMs is a major challenge. In this presentation, we show that dissolving Ni4Ti3 nanoprecipitates in Ni-rich NiTi SMAs via up-quenching can create the required nanoCMs. Using phase-field simulations, we investigate the effects of Ni4Ti3 nanoprecipitate microstructure and up-quenching parameters (temperature and time) on the characteristics of the nanoCMs (amplitude and wavelength) as well as the corresponding stress-strain behavior, including the size of hysteresis, linearity, and apparent elastic modulus.