High temperature deformation behavior and processing map for a nickel-titanium shape memory alloy

The hot deformation behavior of 49.2Ti-50.8Ni shape memory alloy was studied using hot compressive deformation testing in the temperature range of 1023-1323 K and at strain rates of 0.01-10 s(-1). The work-hardening rate was induced to analyze the stress-strain curves, and the critical stress sigma c and the dynamic recovery saturation stress sigma(sat) were measured which can be specified approximately by the expressions: sigma(sat)-1.12 sigma(p) and sigma(c)-0.86 sigma(p). An Arrhenius model was calculated to describe the relationship between peak stress and the Z parameter. The relationship between deformation activation energy, the deformation conditions and the effect of Ni component in a binary TiNi alloy on the activation energy were discussed in this work. With the help of electron backscattering diffraction, a connected mode dynamic recrystallization microstructure was confirmed in peak efficiency regimes (850 A degrees C & 0.01 s(-1) and 1050 A degrees C & 10 s(-1)) of the processing map.