Design of Porous Shape Memory Alloys with Small Mechanical Hysteresis

The mechanical hysteresis loop behavior always limits the applicability of shape memory alloys (SMAs) in mechanical devices requiring high sensitivity, durability and energy conversion efficiency. In this study, through experiments and finite element simulations, we systematically investigated the effects of porosity and pore distribution on the mechanical hysteresis behavior of porous Ti49.2Ni50.8 SMAs. Inspired by atomic crystal structures, some porous SMAs with ordered void distributions were investigated to compare them with SMAs with random pore distributions. Our results show that the hysteresis reduces with increasing porosity in porous SMAs. The designed BCC-type ordered porous SMAs possess a narrower hysteresis loop with less energy dissipation at the same porosity. The gradual and homogenous martensitic-phase transformations are responsible for this characteristic. The present work provides an effective way to design porous SMAs with narrow hysteresis, which is promising in applications for mechanical sensors or actuators.