Relationship between the hardening phenomena on welding heat-affected-zone and the tensile property in SUS316L stainless steel

The dynamic strain aging phenomena is believed to be one of the important mechanisms which harden the weld heat affected zone of low carbon austenitic stainless steels. Hence, we investigated the effects of test temperature and the strain rate during tensile tests on the dynamic strain aging of type 316L strainless steel (SS) in this study. The results obtained are as followings; (1) Two types of stress-strain curves were obtained with regards to the serration caused by the dynamic strain aging in the tensile tests with different test temperatures and strain rates, one with high frequency of the serration and the other with low frequency. (2) The area where the serration being observed was determined by two lines showing the temperature dependency of the strain rate in the form of e=Aexp{-Q/(RT)}, where A: constant, Q: apparent activation energy (150 kJ/mol or 290 kJ/mol), R: gas constant, T: absolute temperature. (3) The increase in micro-Vickers hardness of type 316L SS after being strained to certain strains showed maximum values determined by the combined effect of the test temperature and the strain rate. The largest increase in the hardness was obtained at the condition of the lowest temperature and strain rate among the test condition. (author)