Tensile deformation of NiTi shape memory alloy thermally loaded under applied stress

• DOI: 10.1016/j.matdes.2023.111638
• Publication Date: 2023-01-20T17:21:00Z
• Authors: P. Šittner; E. Iaparova; L. Kadeřávek; Y. Chen; O. Tyc
• Keywords: Nickel titanium; Isothermal process; Diffusionless transformation; Stress–strain curve

Constitutive behavior of engineering materials is typically characterized by stress–strain curves from isothermal tensile and/or compression tests until fracture. Strain reversible martensitically transforming shape memory alloys (SMA) additionally cyclic and strain-temperature limited to temperatures stresses, at which the recorded strain responses are in closed loop cycles. In this work focussing coupled martensitic transformation plastic deformation NiTi, we deformed nanocrystalline NiTi SMA wire isostress beyond temperature stress limits stemming requirement on reversibility tests. Stress–strain-temperature such were analysed. To detect characterize mechanisms activated performed thermomechanical loads, electric resistance dynamic elastic modulus evaluated in-situ during Martensite variant microstructures lattice defects austenite evolving upon heating under 750 MPa analyzed post mortem transmission electron microscopy. Stress-temperature diagram showing critical stress–temperature conditions for activation 5 different deformation/transformation processes thermomechanically loaded was constructed results stress–strain-temperature discussed based