Effect of high strain rate deformation on the properties of SS304L and SS316LN alloys

Abstract

Effect of high strain rate deformation on the properties of SS304L and SS316LN alloys has been studied using Split Hopkinson Pressure Bar (SHPB) in the strain rate regime of 7 × 102–3 × 103. The results indicate towards a higher rate of increase in flow stress for SS304L steel as compared to SS316LN with increasing the strain rates. The results corroborate well with the extent of strain induced volume fraction of martensite, as measured using Magnetic Barkhausen Emission (MBE) technique. The steep increase in strength of SS304L at low strain e.g., < 5% and strain rate up to ∼1.8 × 103 s−1 is attributed to strain induced martensitic transformation. Whereas, SS316LN remains mostly nonresponsive in the strain induced phase transformation process in the entire strain rate regime. Both the materials have shown a poor strain hardening behaviour. Up to the strain rate 1.8 × 103 s−1 a growth of 23% and 18.5% of hardness value was observed in SS304L and SS316LN materials respectively. As the strain rate is further increased, hardness value in case of SS304L material has shown a decreasing trend, while that of SS316LN material has shown an increasing trend. The experimental observation has been tried to explain in terms of strain induced changes in their lattice structure that occur in the respective materials due to mechanical impact and their respective chemical composition.