The Cyclic Stability of Superelasticity in Aged Ti49.3Ni50.7 Single Crystals with Oxide Surface

The cyclic stability of superelasticity in compression [001]B2-oriented Ti49.3Ni50.7 single crystals is considered this paper. were aged at 823 K for 1.0 h air and helium. It has been experimentally shown that a two-layered surface thin film, consisting Ni-free oxide layer Ni-rich sublayer, appears after the oxidation air. layers have weak effect on forward B2-R-B19’ martensitic transformation temperatures: TR temperature increases by 4 K; Ms Mf temperatures decrease 6 K. does not affect either response during fatigue tests or reverse B19’-B2 transformation. cracking was found This contributed relaxation internal stresses. Such stresses are caused both formation an aging matrix deformation stress-induced main mechanisms oriented growth Ti3Ni4 precipitation near film air, dislocations precipitation-matrix interface fine twinned B19’-martensite tests.