Ti-Ni-Nb(-Zr) shape memory alloys with wide martensitic hysteresis

• Published in: Metalurgija Vol. 45; no. 3; p. 213
• Main Authors: Khmelevskaya, I Yu, Abramov, V Ya, Aleksandrova, N M, Borovkov, D V, Makushev, S Yu, Polyakova, N A, Popov, N N, Prokoshkin, S D
• Format: Journal Article
• Language: English
• Published: 01.07.2006
• ISSN: 0543-5846

The alloys: 45 at % Ti-45 at % Ni-10 at % Nb (1) and 42,6 at % Ti-46,5 at % Ni-8,0 at % Nb-2,9 at % Zr (2), which are used for thermomechanical couplings (TMC) were investigated. It was shown that high-temperature thermomechanical treatment (HTMT) at 800 deg C, epsilon=0,3 creating dynamically polygonized substructure leads to improvement of functional properties of Ti-45%Ni-10%Nb alloy in comparison with the conventional quenching: the shape recovery rate increases by 10% and the recovery stress reaches 1000 MPa in comparison with quenching. Doping of Zr leads to improvement of functional properties and widening of hysteresis of martesite transformation. The HTMT leads also to decreasing of the recovery stress relaxation temperature on cooling lower -20 deg C for alloy 1 and lower-50 deg C for alloy 2. A rather high shape memory effect (SME) also induces a two-way SME (TWSME) in Ti-Ni-Nb alloys which value reaches epsilonlw=1 to 2% when the SME inducing strain is higher than 5%. Such TWSME value is enough for the TMC self-dismantling during deep cooling.