Intergranular Fracture at 500℃ in Pre-Fatigue Crack Tip Damaged Zone of Austenitic Stainless Steel

摘要

The present work was carried out to study the effect of fatigue crack tip damage on the following high temperature fracture initiation behaviour. Compact tension specimens of type 321 stainless steel were pre-fatigue cracked at room temperature RT and at 123℃. The specimens were tensile loaded to fracture initiation at 500℃ at cross head speed of 0.1-0.001mm/min. Scanning electron microscopic observation of the fracture surface revealed the occurrence of the intergranular fracture at the fracture initiation region at slow strain rate and not at high strain rate. The zone of the intergranular fracture increased with increasing the pre-fatigue stress intensity factor. It was found that the fatigue crack tip damaged zone enhances the susceptibility of the intergranular fracture at high temperature slow strain tension.