The Effect of Vanadium on the Superelastic Properties of FeMnAlNi Shape Memory Alloy

The FeMnAlNi Shape Memory Alloy (SMA) holds significant potential for many applications as it exhibits superelastic (SE) properties across a wide temperature range with high transformation stresses. This Fe-based system offers an economical alternative for costly SMA such as NiTi while offering superior damping characteristics. However, only a limited number of compositions based on the FeMnAlNi system have been considered in the literature. This study explores the enhancement of superelastic properties in FeMnAlNi through alloying with vanadium. Two compositions, Fe₄₂Mn₃₄Al₁₅Ni_7.5V_1.5 and Fe₄₂Mn₃₄Al_12.5Ni_7.5V₅ (at.%), were prepared and various cyclic heat treatment and aging processes were considered aiming to increase the transformation stress levels. Vanadium addition stabilized the BCC austenitic phase, suppressed the γ-phase precipitation, and promoted the development of a coarse-grained structure that is conducive to superelasticity. At 5-at.% V, a stable BCC phase with large grains was obtained, but no significant reversible transformation was observed at all the considered heat treatments. However, at 1.5-at.% V, SE was achieved, with transformation stress varying by aging conditions. The highest transformation stress of approximately 1,090 MPa, a record for FeMnAlNi-based SMAs, was obtained under optimized aging conditions. These findings highlight the role of vanadium in tailoring superelastic properties in FeMnAlNi SMAs.