Effects of thermo-mechanical treatment on a Fe-13Mn-5Si-12Cr-5Ni shape memory alloy

摘要

Effects of thermo-mechanical treatment on the microstructure, precipitation behavior and shape memory performance of a Fe-13Mn-5Si-12Cr-5Ni shape memory alloy were investigated. Experimental results show that the deformation-induced defects, such as dislocation bands, stacking faults and γ/ε interfaces are preferential sites for nucleation of the precipitates during aging at 500～600°C. The precipitate is identified to be η carbide (M_2C), exhibiting an orthorhombic structure with lattice constants of a=4.704A, b=4.318A and c= 2.830A. The orientation relationship between the γ austenite and η precipitate is [020]γ//[111]η, <020>γ//<111>η. The as-cold-rolled specimen has a worse shape recovery. After 500～600°C aging, both effective nuclei and well-aligned precipitates within the grain interior will cause the single variant of stress-induced ε martensite to form, thus the shape memory effect is significantly improved. But for 700～900°C aging, the disappearance of both effective nuclei and well-aligned precipitates will obviously reduce the specimen's shape memory performance.