Topical seminar on structure and dynamics of crystals

02-05-2026 11:00 DNICM conference hall, bldg. 42а FLNP

"NiTiHf high-temperature shape memory alloys"

Shuitcev Aleksandr Vladimirovich 

Harbin Engineering University (Harbin, China)

Shape memory alloys (SMAs) attract a lot of attention from engineering fields because of their superior functional properties, such as shape memory effect and superelasticity. Those properties result from reversible thermoelastic martensitic transformation (MT), which can be thermally or stress induced. Unfortunately, for the most commercially successful binary NiTi SMAs MT temperatures below 100 °C. The addition of Hf allows to increase the MT temperature in NiTi alloy. Unfortunately, the strain recovery properties of ternary NiTiHf high-temperature SMAs are far from theoretically predicted values. It is commonly accepted that low shape memory and superelasticity in NiTiHf are caused by the low dislocation slip stresses that prevent reversible strain recovery. Thus, the main strategy for improving the functional properties of high-temperature SMAs is to increase the stress levels of dislocation motion. This report presents the results of a study of the effect of various strengthening mechanisms (precipitation strengthening, grain refinement and solution strengthening) on the structure and properties of NiTiHf high-temperature SMAs.