Effect of dynamic strain aging on high temperature properties of austenitic stainless steel

Abstract

Abstract 18-8 type austenitic stainless steel has been subjected to tension test at a range of strain rates (5×10−4–5×10−2 s−1) and temperatures ( 298–973 K ) to investigate the effect of temperature and strain rate on its mechanical properties. It was found that the serrated flow behavior of this material, one of the evident features of dynamic strain aging (DSA) phenomenon can be divided into two sections according to the temperatures, i.e. the range of 523–673 K and 723–873 K at the strain rate of 5×10−4 s−1. Within these two temperature ranges, one can find some similar rules, for example, the critical strain ec for the onset of serrations reduces with increasing temperature. By calculating the activation energy of the DSA process of the material, it is found that the DSA at lower temperature range is caused by the interaction between (C, Ni) solute atom atmosphere and dislocation, and the DSA at higher temperature range is caused by the interaction between (C, Cr) solute atom atmosphere and dislocations. In order to further investigate the influence of DSA on high temperature strength of the material, the static tensile tests at temperatures of 573, 723, and 873 K, creep tests were also carried out, respectively, after various DSA pre-treatments and cold-working processes. The results show that the high temperature short-time strength and 873 K creep rupture strength of the specimens increase with increasing pre-strain temperature and pre-strain, and the strengthening effect of DSA is higher than that of cold-working at the same pre-strain.