析出相对317L不锈钢力学性能的影响OACHSSCD

317L stainless steel is a high-molybdenum austenitic stainless steel widely used in petrochemical,chemical,and nuclear engineering.However,during prolonged high-temperature service,hard and brittle phases,such as σ phase and carbides,can precipitate.This leads to a degradation of mechanical properties and threatens the safety of engineering structures.This study examines the impact of aging temperature(750 and 850 ℃)and aging time(25-500 h)on the types and amounts of precipitated phases,as well as on the mechanical properties of 317L stainless steel.The results show that the residual δ-ferrite in steel promotes rapid nucleation of the main precipitation phase(σ phase),and the amount of precipitation increases significantly with longer aging time and temperatures.Precipitation induces hardening,resulting in a significant increase in the hardness of the material after aging.The hardness change is positively correlated with the volume fraction of precipitation phases.However,the ductility and toughness of the material are seriously deteriorated.The precipitation phases(especially σphase)can not only strengthen the matrix by pinning dislocations,but also act as sites for brittle cracks,leading to grain boundary embrittlement.This results in a transition from ductile to brittle fracture.