Shape Memory Behavior in Some (Ti,Zr,Hf)50(Ni,Cu)50 Alloys Elaborated by Glass Devitrification
A series of multielementary AB-type shape memory alloys, quaternary (Ti,Hf)50(Ni,Cu)50 and quinary (Ti,Zr,Hf)50(Ni,Cu)50, have been produced by means of the melt-spinning (ribbons), twin-roll casting (strips) and injection casting (bars) techniques. The glass forming ability (GFA) has been investigated by means of calorimetric studies (DSC, DTA), microscopic observations (TEM/SAD, SEM, XRD, optical microscopy) and deformation tests (bending, tension). The glass transition (Tg) and crystallization (Tx) temperatures with the corresponding supercooled liquid window ΔT = Tx – Tg have been determined for the mentioned rapid solidification techniques. GFA is found to be strongly dependent on specific ratio between the constituent alloying elements, with effective element A containing mixture of the early transition elements A = (Ti,Zr,Hf) and effective element B containing mixture of the late transition elements B = (Ni,Cu), respectively. We report a choice of the alloy composition, which is amorphous after fast cooling while recovers a reversible B2 ↔ B19 ↔ B19' martensitic transformation sequence and demonstrates shape memory and superelastic properties (up to MS ~ 400 K, AF ~ 450 K in the bulk material versus MS ~ 250 K, AF ~ 350 K in the ribbon and strip states) after an adequate thermal treatment.
Pietro VINCENZINI and Stefano BESSEGHINI
V. I. Kolomytsev et al., "Shape Memory Behavior in Some (Ti,Zr,Hf)50(Ni,Cu)50 Alloys Elaborated by Glass Devitrification", Advances in Science and Technology, Vol. 59, pp. 113-118, 2008