On the nature of anomalously high plasticity of high-strength titanium nickelide alloys with shape-memory effects: II. Mechanisms of plastic deformation upon isothermal loading

Abstract

Mechanisms of plastic deformation have been studied in detail in the process of isothermal loading at room temperature in a high-purity shape-memory alloy of composition Ti49.4Ni50.6. The alloy was studied in two initial states: usual coarse-grained (with an average grain size of 20–30 μm) and submicrocrystalline (with an average grain size of 0.2–0.3 μm). It has been shown that during tensile tests there occurs a mechanically induced martensitic transformation in the alloy at stresses corresponding to stages I, II, and III in the tensile curve and then elastic and plastic deformation of B19′ martensite is observed at stages IV, V, and VI, respectively. Optical metallography in situ and electron microscopy have been used to study microstructural features and mechanisms of plastic deformation of the alloy up to its failure.