Orientation and temperature dependence of superelasticity caused by reversible γ-α′ martensitic transformations in FeNiCoAlTa single crystals

Abstract

Reversible thermoelastic γ-α′ martensite transformations (MTs) have been studied in Fe-28%Ni-17%Co-11.5%Al-2.5%Ta (at. %) single crystals under cooling/heating and loading conditions. It is established that the precipitation of dispersed γ′ phase particles with an average size of d ≤ 5 nm leads to thermoelastic γ-α′ MTs with a small temperature hysteresis (ΔT = 20 K). The [001] oriented crystals favor the attaining of maximum superelasticity (SE) ɛSE = 6.8%, minimum mechanical hysteresis Δσ = 130 MPa, and large SE temperature interval ΔTSE = 130 K. In contrast, in the [111] oriented crystals, small values of ɛSE = 2.0%, high values of Δσ = 350–400 MPa and narrow SE interval ΔTSE = 55 K are found.