Effect of grain boundary precipitation on low-cycle fatigue behavior aat elevated temperature of SUS 316 stainless steel

SUS 316鋼 의 高溫低사이클 피勞擧動 에 미치는 粒界절出物 의 影響

The temperature and the grain boundary precipitation have the great influence on the low-cycle fatigue behavior of austenite stainless steel at elevated temperature. For the purpose of investigating the mechanism concerning the change of fatigue micro crack mode in SUS 316 under various conditions low-cycle fatigue test was carried out at the elevated temperature 600.deg.C, plastic strain range 2% and constant strain rate .5c.p.m. A special attention is given to the observation of intergranular crack initiation. The results obtained are summarized as follows. The low-cycle fatigue behavior of SUS 316 at 600.deg.C is affected by transition of crack initiation mode from intergranular to transgranular. The transition is due to the aging effect, which is caused by grain boundary precipitations of Cr$\_$23/C$\_$6/. Since the intergranular crack initiation is brought about by the grain boundary sliding, the transgranular crack initiates in case that the strengthening of grain boundary due to the precipitation of Cr$\_$23/C$\_$6/ carbides takes place ahead of the intergranular crack initiation.