Improved superelasticity and fatigue resistance in nano-precipitate strengthened Ni50Mn23Ga22Fe4Cu1 microwire

Abstract Smart shape memory alloy applied for driving and sensing devices requires reversibility and repeatability. However, the inherent intergranular brittleness of Ni-Mn-Ga shape memory alloy induced poor fracture resistance and insufficient cyclic fatigue life has been the stumbling block for its industrial applications. Here, we develop a dual-phase shape memory microwire with superior large reversible strain and extraordinarily fatigue resistance. The reversible phase transformation can be induced by the stress upon 200 MPa with larger than 10% reversible strain, and at least 104 transformation cycles are stably achieved at room temperature. The High-resolution TEM results show that ~3% content of the uniform precipitates of γ phase is embodied in the austenitic matrix. It acts as a beneficial role to ensure the reproducible transformation stability from the result of In-situ TEM. This study paves the way for designing fatigue resistance long fatigue life shape memory alloys by the synergy of multiphase.