On the tensile flow stress response of 304 HCu stainless steel employing a dislocation density based model and electron backscatter diffraction measurements

Abstract

ABSTRACTTensile flow stress response of 304 HCu stainless steel is investigated using a dislocation density based model and electron backscatter diffraction (EBSD) studies. The model considers two types of dislocations explicitly, i.e. mobile and forest, to model the flow behaviour in the temperature range 300–973 K, at strain rates 3×10 −3 and 3×10 −5 s-1. The flow behaviour indicates the predominance of thermal recovery at higher temperatures, except at 923 K/3 × 10−5 s−1. The dislocation model predicts a rapid increase in both mobile and forest dislocation densities at the early stages of deformation and thereafter reach saturation/steady state. Higher strain rate leads to an increase in dislocation densities with concomitant increase in peak flow stress, indicating significant dislocation multiplication. The dislocation densities decreased with an increasing temperature and is attributed to thermally activated recovery by glide (slip and cross-slip) and climb of dislocations. However, an offset to the thermal recovery is observed at 873–923 K at 3 × 10−5 s−1 wherein the magnitudes of peak flow stress, boundary and forest dislocation densities are of similar magnitude at both the temperatures, thereby signifying the occurrence of matrix hardening by DSA and precipitation. Boundary dislocation densities estimated from EBSD data have shown affinity to that of predicted forest dislocation densities.