Trigger for the occurrence of grain coarsening phenomenon of BS304S31 austenite stainless steel under small plastic strain at high temperature

摘要

Observation by optical microscopy and EBSP have made it ckar that the trigger for the grain coarsening phenomenon of austenite stainless steel BS304S31 may be the stacking faults concentrating selectively in a thin layer lying just beneath the grain boundary. When macroscopic plastic strain reached 6 percent, selective concentration of stacking faults was observed. When it reached 20 percent, the distribution of stacking faults became uniform in each grain. After these specimens were heated, concentration of stacking faults disappeared, and grain coarsening occurred at the point with 6 percent strain, but no grain coarsening occurred at the point with 20 percent strain. In order to investigate this concentration of stacking faults, an attempt was made to analyze the deformation in each crystal by using image-based FEM. The result suggested that there is a possibility that plastic strain concentrates in the vicinity of the grain boundary when the macroscopic plastic strain is small.