13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- Other damage behaviour in AISI 316L is shown in fig.4. At room temperature the deformation and damage behaviour is similar for strain rates of 2*10-3/s and 10-6/s. Common damage appearing away from fracture zone is slip bands creating voids when intersecting with each other, grain boundaries or precipitates. Voids due to intersection between slip bands and grain boundaries, around 15mm away from the fracture surface are displayed in fig. 4 a). Voids also occur due to heavy deformation from shear bands as in fig.4 b). Near the fracture surface the microstructure is heavily deformed from multi-direction slip bands, shear bands and planar slip. Deformation bands with features looking like subcells appear near the fracture surface at room temperature for strain rates of 2*10-3/ and 10-6/s. At elevated temperature the deformation bands look recrystallized as can be seen in fig. 4 c) and d). The EBSD analysis in fig.5 reveals that the areas that look like recrystallization has taken place (see fig.5 a)) don’t show any new grains in AISI 316L at 650°C and a strain rate of 10-3/s. Fig.5 b) shows the local misorientation in gray scale together with inversed pole figure (IPF) in color scale, and the brighter patterns correspond to local misorientation values above 4° and up to 5°. These brighter patterns have good correlation to some of the subcell or grains that can be seen in fig.5 a). The crystallographic orientation differs but doesn’t give clear distinction between the supposed subcells or grains and the matrix and thus no evidence of recrystallization is found. The analysis in fig.5 is made in mostly one single grain or annealing twin, showing precipitates in the grain boundaries as white zero-solution in fig.5 b). Figure 4. Deformation and damage behavior by ECCI in AISI 316L materials, a) voids from interaction between slip bands and grain boundaries (GB) at RT and strain rate 2*10-3/s, b) void due to deformation from shear band at RT and 10-6/s, c) subcell band (SuB) at 650°C and 10-6/s and d) magnification of subcell band. Crack in GB Void Void SuB SuB a) b) Shear Band Load direction Load direction Precipitates GB 2 μm 1 μm 25 μm 1 μm c) d)
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