150 R.F. Hamilton et al. Fig. 19.6 (a) The stress-strain response at 60 ıC, the material is deformed to 8 % average strain and unloaded. (b) After unloading, the straintemperature response during heating at null load. Inset images of strain contours are shown along selected points on both curves. The strain is in the loading direction. In part (b), the scale has been adjusted to highlight the changes in strain contours during heating Fig. 19.7 The stress-strain response when annealed material is deformed at RT along with accompanying DIC strain fields at selected points. The strain in the deformation fields is calculated in the loading direction The RT response of a solution annealed specimen is shown in Fig. 19.7. The accompanying DIC deformation fields along selected points during the deformation are also shown. During the initial elastic response, the strains in the DIC deformation fields increase homogeneously. The curve deviates from linearity around an average strain of 1 % and strains continue to increase uniformly across a large region in the gage section till an average strain of around 1.6 %. At an average strain of 1.6 %, there is a stress drop and a localized band appears towards the bottom of the specimen. As the specimen is loaded, the uppermost boundary of the band grows towards the top of the specimen. The strains outside the bands remain unchanged, while the strains within the band increase slightly to around 10 %. This band grows as the deformation proceeds throughout a stress plateau. At an average strain of 3.2 %, the specimen fractures. The fracture initiates at the uppermost boundary of the high strain region. 19.4 Conclusions In this paper, the effects of test temperature on the full-field deformations of Ni47.7Ti43.5Nb8.8 (at%) rolled strip material have been characterized. Both the RT and 60ıC stress-strain loading responses are accompanied by a stress-drop and a transition onto a stress plateau via the formation of a high strain band that grows. The behavior can be attributed to the initiation of the stress-induced forward MT. Throughout the stress plateau, at both temperatures, the local transformations measured using DIC analysis reach about 13 %. On the other hand, the average strain determined from the crosshead displacement is set to
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