Issue34

S. Takaya et alii, Frattura ed Integrità Strutturale, 34 (2015) 355-361; DOI: 10.3221/IGF-ESIS.34.39 357 R ESULTS AND DISCUSSION Stress corrosion cracking (SCC) under the cathodic potential of -1.4V ig. 3 shows the fracture surfaces of SCC test under the cathodic potential of -1.4V [5]. Fig. 3(b) is the magnified view of fracture surface at K =23.7MPam 1/2 . It should be noted that parallel lines are recognized near the edge of specimen surface. As shown in Fig.3(c), the areas with parallel lines are classified into three areas, I, II and III. The angle between the parallel lines and horizontal line was 89º, 65º and 80º for the area I, II and III, respectively. Vickers indentations were put around the lines (see Fig.4(a)) and the change of the size of Vickers indentation before and after polishing gave the depth of polishing around 10 to 20 μm. Fig. 5(a), (b) and (c) show the EBSD analytical results in the areas I, II and III, respectively. Due to the limitation of the polishing depth, low CI (Confidence Index) value area is relatively wide in all observations. But the grain orientations in all figures are identified from the areas with high CI values. First, it should be noted that twining was not found in all areas. Figure 3 : SEM micrographs showing SCC fracture surface tested under the cathodic potential of -1.4V; (a) Macroscopic appearance, (b) Magnified view showing parallel lines, (c) Classification of the areas with parallel lines. Figure 4 : Vickers indentation around parallel lines; (a) Before polishing, (b) After polishing. F (c) (I) (II) (III) (a) (b) (c) (a) (b)