Effect of Annealing Temperature and Strain Rate on Mechanical Property of a Selective Laser Melted 316L Stainless Steel

摘要

In the present work,316 L stainless steel specimens are fabricated by selective laser melting(SLM)via optimized laser process parameters.The effects of two extrinsic factors,i.e.,strain rate and annealing temperature,on the mechanical performance of SLM-processed parts are studied.The two intrinsic factors,namely strain rate sensitivity m and work hardening exponent n,which control the tensile properties of the as-built samples,are quantified.Micro structure characterizations show that cellular structure and crystalline grain exhibit apparently different thermal stability at 873 K.Tensile testing reveals that the yield strength decreases from 584±16 MPa to 323±2 MPa,while the elongation to failure increases from(46±1)%to(65±2)%when annealing temperature varies from 298 K to 1328 K.The n value increases from 0.13 to 0.33 with the increase in annealing temperature.Due to the presence of fine cellular structures and high relative density achieved in as-printed 316 L samples,a strong dependence between tensile yield strength and strain rate is observed.In addition,the strain rate sensitivity of the SLM-produced 316 L part(m=0.017)is much larger than that of conventional coarse-grained part(m=0.006),whereas the n value increases slightly from 0.097 to 0.14 with increasing strain rate.