Increase of Low Cycle Fatigue Life at 300 degC for Type 304 Stainless Steel

摘要

Tensile, low cycle fatigue, and fatigue crack growth rate tests were conducted at RT and 300 deg C for type 304 stainless steel. Tensile was tested under displacement control and low cycle fatigue was tested under strain control. Fatigue crack growth rate test was conducted under load control and crack was measured by DCPD method. Yield strength and elongation decreased at 300 deg C. Dynamic strain aging was not detected at 300 deg C. Low cycle fatigue life increased but fatigue strength decreased at 300 deg C. Fatigue crack growth rate increased at 300 deg C. Dislocation structures were mixed with cell and planar and did not change with temperature. Grain size did not change but plastic strain increased at 300 deg C. Strain induced martensite after low cycle fatigue test increased at RT but decreased at 300 deg C. It was concluded that the increase of low cycle fatigue life at 300 deg C was due to the decrease of strain induced martensite at which crack was initiated.