Effects of long-term thermal aging on elevated temperature deformation behaviors of wrought 316LN stainless steel by small punch test

Abstract

The deformation behaviors of as-received and thermal aged wrought 316LN austenitic stainless steel (ASS) were investigated at 350 °C by small punch test (SPT) in order to evaluate the effects of long-term thermal aging on the elevated temperature deformation behaviors of the wrought ASS. The results showed that long-term thermal aging at 400 °C had obvious influences on the density and structure of dislocations, hence affecting the deformation mechanism and mechanical behaviors. There were many planar slip bands and tangled dislocations in the as-received wrought 316LN ASS, while, a low-density dislocation multiples, coplanar dislocation arrays, stacking faults and extended dislocations were formed due to the microstructure recovery during the long-term thermal aging. Correspondingly, both dislocations slip and deformation twinning played an important role in plastic deformation in the as-received wrought 316LN ASS, while interaction of dislocations and stacking faults inclined to dominate the plastic deformation process of the thermal aged 316LN ASS under the elevated temperature. As a result, long-term thermal aging resulted in the change of the mechanical properties of the wrought 316LN ASS. The hardness and SPT maximum load of 316LN ASS had a slight increase, while the SPT total energy exhibited a reverse trend with increasing aging time, indicating that the 316LN ASS showed a tendency of hardening after the long-term thermal aging.