Achieving near zero-hysteretic superelasticity in a Ni43Fe18Ga27Co12 single-crystalline microwire via Lüders-like phase transformation

摘要

Ni43Fe18Ga27Co12 single-crystalline microwires directly fabricated by the Taylor liquid drawing method show the nature of a strong first-order martensitic transformation under external stress or load-biased temperature cycling. By eliminating the nucleation energy barrier through localized plastic deformation, a fully recoverable supere-lastic strain approaching 11 % with negligible hysteresis is achieved in the course of tensile deformation. Based on in-situ synchrotron high-energy X-ray diffraction analysis, the mechanism of nearly non-hysteretic trans-formation is unraveled as a sharp, Luders-like phase transformation. It is found that a single martensitic domain propagates continuously in a monolithic fashion under superelastic cycling with poor crystallographic compat-ibility of lambda 2 = 0.950 and small volume change of Delta V =-0.17 % accompanying martensitic transformation. We attributed such near zero-hysteretic transformation characteristics to combining conditions of low crystal defect density, high nucleation barriers but without continual nucleation events, flexibility of the microwire, and small volume change.

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