Achieving high strength and large recoverable strain by designing honeycomb-structural dual-shape-memory-alloy composite

Abstract

Developing shape memory alloys (SMAs) with high strength and large recoverable strain is meaningful to broaden their application in extreme scenarios. In this work, a dual-SMA composite with bio-spired honeycomb structure, which consists of NiTi SMA matrix and NiTiZrCu SMA reinforcement, was designed and fabricated through the combination of 3D printing and hot extrusion. The utilization of honeycomb structure ensures uniform stress transmission and reducing the likelihood of stress concentration. The resulting microstructure, martensite transformation, and superelasticity were studied systematically. The dual-SMA composite exhibited a superior superelasticity with a remarkable recoverable strain higher than 5% and good recovery rate of 96% under a high external stress of 1.4 GPa. Fundamentally, the honeycomb structure in the dual-SMA composite facilitates the occurrence of progressive phase transformation process. The large recoverable strain and good recovery rate were attributed to the coupling effect of superelasticity and linear-elasticity throughout the whole loading process, which enables the dual-SMA composite to sustainably bear the load without undergoing plastic yielding. These findings make it available for designing and fabricating SMA composites with superior performance.