The relationship between work hardening and the nature of serrations observed in a 15Cr-15Ni-2.3Mo-Ti modified austenitic stainless steel during tensile testing

The variation of work hardening rate (WHR) on the serrations has been analy sed with respect to the type of serrations for a 15Cr-15Ni-2.3Mo-titanium m odified austenitic stainless steel in the temperature range 300 to 1023 K. The results showed that the WHR, its rate sensitivity and the nature of ser rations are strongly related. A clearly periodic locking type serrations oc curred under conditions where the material in general exhibited high WHRs a nd when the WHR has a small positive rate sensitivity, as at low temperatur es and at high strain rates. The serrations changed over to partial or full y unlocking serrations under conditions when WHRs would be lowered due to s train induced or thermally assisted recovery processes, and the rate sensit ivity of the WHR becomes very large, as seen at high temperatures, large st rains and low strain rates. At still higher temperatures, the serrated flow ceases when the WHR becomes negligible. It is concluded that under conditi ons of high WHR and low rare sensitivity of WHR periodic locking type serra tions occur and under conditions of low WHR and high rate sensitivity of WH R unlocking type serrations occur.