Gaining flexibility in the design of microstructure, texture and shape memory properties of an Fe-Mn-Si-Cr-Ni alloy processed by ECAE and annealing

Abstract

The effect of ECAE on the properties of an Fe-15Mn-5Si-9Cr-5Ni shape memory alloy (SMA) was investigated. Phases, texture, microstructure, critical temperatures, mechanical and SM properties after severe deformation, and the effect of annealingwere analysed. One ECAE pass develops a shear texture. There is a large 〈101〉 component in the extrusion direction,which is near the ideal 〈414〉 for martensitic transformation activation. The pressing did not refine the previous as cast structure but introduced dislocations and ε-martensite. Thus, the stress to induce the Γ → ε martensitic transformation, σΓ → ε, reached 620 MPa, and the quantity of ε-martensite formed after compression was limited. The degree of shape recoverywas reduced,while the reverse transformation temperatures increased. Heat treatments above 800 ° C activated recrystallization. As annealing temperature increased, new grains nucleated and grew, reaching a size of 53 μm after heating to 1000 ° C. For this condition,σΓ → ε was 430 MPa, and the best shape recovery was achieved, 64%.