Issue 33

M. Sakane et alii, Frattura ed Integrità Strutturale, 33 (2015) 319-334; DOI: 10.3221/IGF-ESIS.33.36 330 activation. At elevated temperatures, dislocations glide more easily to form a structure with low elastic energy by the assistance of thermal activation so that a ladder or maze structure, which is a lower elastic energy microstructure than the cell, was found. In Case 5, which is a proportional straining, Fig. 18 (e), cell structures were observed. A deformation twin boundary was also observed at the center of the photograph. Diffraction pattern were taken for all the dislocation structures but it is difficult to distinguish between stacking fault and martensite that was observed by McDowell et al. [13]. Figure 16 : Shear stress-axial stress hysteresis loops under 14 strain waveforms. Case 7, Fig. 18 (f), shows a coherent boundary of an annealing twin at the center of the photograph. Its role is similar to a grain boundary for the deformation microstructure. Dislocation walls are observed in the right of the photograph, and a cell structure is found in the left of the photograph. In Case 7, columnar cells were formed and Fig. 18 (f) shows the two