Enhancement of Superelasticity in Fe-Ni-Co-Based Shape Memory Alloys by Microstructure and Texture Control

Fe-Ni-Co-based shape memory alloys (SMAs) enjoy a wide application prospect in seismic protection structures or components owing to their advantages of high strength, excellent cold workability and low material cost. In this study, the effects of microstructure and grain orientation on the shape memory effect (superelasticity) were investigated, which could offer theoretical guidance for microstructure and texture control during the fabrication process of high-performance Fe-Ni-Co-based SMAs. The results showed that, the recoverable strain values by theoretical calculation of the alloy on <100>, <101> and <111> orientations were 9.1%, 7.4% and 1.2%, respectively, and the recoverable strain became maximum near the grain orientation of <100>. For improving the shape memory performance, both the directional solidification technology and rolling + recrystallization technology could be adopted to effectively control the formation of the microstructure with strong <100> grain orientation. Based on this, an equiaxed-grained Fe-Ni-Co based SMAs with strong {lik0}<001> texture was prepared by 98.5% rolling deformation, recrystallization at 1220 degrees C for lh and aging treatment at 600 degrees C for 96h. It exhibited superelastic strain of 3.2%, residual strain of 0.7%, and tensile strength of approximately 960MPa. Compared with the conventional forging Fe-Ni-Co-based SMAs (without superelasticity), the superelasticity of the alloy fabricated by microstructure and texture control was enhanced significantly. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on the Technology of Plasticity.