13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- HAZ Plate thickness direction Stress Gr.122 steel weld t/tr=0.98 Figure 3. Binary images of creep voids and cracks observed in the HAZ of a central cross-section of the L-welded joints for the Gr.91 steel crept at 600 ˚C and 90 MPa. Figure 4. Changes of the area fraction of creep voids in HAZ during creep of the Gr.91 and Gr.122 steel welds at 600 ˚C. however, the crack growth rate in the accelerated stage was high for the high strengthened Gr.122 steel. The lower creep ductility of the Gr.122 steel is related to these damage behavior. 3.3. Micro-structural changes in HAZ Changes of microstructures of HAZ in the creep-interrupted L-welded joints was observed and KAM and grain boundary length were measured using EBSD. Figure 5 shows the changes in the grain boundary length in the fine-grained HAZ during creep for both steel welds. Here, length of grain boundaries with misorientation from 5˚ to 65˚ is plotted as prior austenitic boundaries. For the
RkJQdWJsaXNoZXIy MjM0NDE=