Shape Memory Effect and Superelasticity of [001]-Oriented FeNiCoAlNb Single Crystals Aged under and without Stress

The two-step ageing of Fe-28Ni-17Co-11.5Al-2.5Nb (at.%) single crystals under and without stress, leads to the precipitation γ′- β-phase particles. Research has shown that γ–α′ thermoelastic martensitic transformation (MT), with shape memory effect (SME) superelasticity (SE), develops in [001]-oriented tension. SE was observed within range from temperature start MT upon cooling Ms, end reverse heating Af, at temperatures Af 323–373 K. It found crystals, particles, a high level elastic energy, ΔGel, is generated, which significantly exceeds energy dissipation, ΔGdis. As result, MT, while As, became lower than Ms. development stress occurs values hardening coefficient, Θ = dσ/dε 2 8 GPa low mechanical Δσ thermal ΔTh hysteresis. reasons for an increase ΔGel during are discussed.