Two-way shape memory effect in stress-induced martensite aged Ni50.3Ti32.2Hf17.5 alloy

Abstract

This study investigated the effect of stress-induced martensite aging on thermoelastic martensitic transformations in Ni50.3Ti32.2Hf17.5 polycrystals containing nanosized dispersed H-phase particles. It was found that stress-induced martensite aging at 428 K for 12 h, under an applied tensile stress of 300 MPa, results in an increase of reversible strain (~37%) with low applied stresses during cooling-heating cycles and induces a tensile two-way shape-memory effect of 2.3% (~50% of the maximum reversible strain). Moreover, stress-induced martensite aging along with detwinning of (0 0 1) compound internal twins under stress provide an increase of temperature intervals of martensitic transformations by 10 ÷ 12 K due to accumulation of elastic energy.