Effects of pre-strain and temperature on impact deformation behaviour of 304L stainless steel

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.This paper employs a compressive split-Hopkinson pressure bar to investigate the impact deformation and fracture behaviour of 304L stainless steel. Annealed 304L stainless steel bars are pre-strained to strains of 0.15 or 0.5 and are machined into cylindrical compression specimens. Impact tests are then performed at strain rates ranging from 2000 to 6000 s-1 at temperatures of 300oC, 500oC and 800oC. The experimental results show that the flow stress increases with increasing pre­ strain and strain mte, but decreases with increasing temperature. Negative and near-zero work hardening rates are found in the specimens pre-strained to 0.5 and then deformed at 300°C and 500oC, respectively. The strain rate sensitivity of the pre­ strained specimens increases with increasing strain rate, but decreases with increasing temperature. The highest strain rate sensitivity is found in the specimen pre-strained to 0.5 and then tested at a temperature of 300°C under a strain rate of 6000 s-1. OM and SEM observations of the fracture surfaces show that the formation of adiabatic shear bands is the dominant fracture mechanism in 304L stainless steel specimens pre-strained to 0.5 and then deformed at temperatures of 300oC or 500oC.