Superelastic response in 〈1 2 2〉-oriented single crystals of FeMnAlNi shape memory alloy in tension and compression

Abstract

The superelastic response of the Fe43.5Mn34Al15Ni7.5 single crystalline shape memory alloy, oriented along the 〈122〉 direction was investigated. The quenched single crystals demonstrated superelastic strains of 4.0% in tension and 2.0% in compression. Ageing at 200 °C for 3 h led to the suppression of superelasticity in compression. An asymmetry in the tension and compression properties, probably associated with the ability of the martensite crystals to detwin under stress, was detected. It is likely that the detwinning of γ′-martensite in compression leads to an increase in the mechanical hysteresis Δσ and the stresses σcr required for the onset of strain associated with the stress-induced martensitic transformation in quenched crystals, suppressing superelasticity in the aged crystals. Tension without the detwinning of γ′-martensite result in a weak influence of coherent B2 (bcc/NiAl) precipitates on the mechanical hysteresis Δσ.