Stress-induced martensitic transformation in high-strength [236]-oriented Ni51Ti36.5Hf12.5 single crystals

The effects of heat treatment on the stress-induced B2-B19' martensitic transformations in the Ni51.0Ti36.5Hf12.5 single crystals oriented along [236] direction are studied. It is shown that in the annealed at 1323K for 4 h crystals, the temperature range of superelasticity increase almost twofold from 75K up to 135K as compared to the as-grown single crystal contained disperse particles of H-phase. The [236]-oriented Ni51.0Ti36.5Hf12.5 single crystals are characterized with high levels of applied compressive stress up to 1700 MPa in the as-grown state and 1900 MPa in annealed crystals for the completely reversible stress- induced B2-B19' martensitic transformation with reversible strain up to |εSE| =1.4%