Monotonic deformation behavior of SA333 Gr-6 steel: Dynamic strain aging

Abstract

The present investigation intends to examine how the dynamic strain aging (DSA) phenomenon affects tensile flow curves, mechanical properties, and dislocation density through tensile loading. Monotonic tensile tests were carried out at room temperature (RT) and elevated temperatures up to 400 °C, whereas the strain rate varied from 1 × 10⁻⁴ s⁻¹ to 1 × 10⁻² s⁻¹. Several features of DSA include serrations on the stress-strain curve, negative strain rate sensitivity, an increase in ultimate tensile strength, and a decrease in ductility with an increase in the temperature of the tensile test. DSA phenomenon was quite evident in a temperature range of 200–350 °C at all the strain rates; nevertheless, the dominant DSA temperature regime was observed between 250 and 300 °C for a slow strain rate of 1 × 10⁻⁴ s⁻¹. However, an increase in the strain rate, the dominant DSA was observed at increased test temperature. Transmission electron micrographs taken post-tensile test revealed that the test conditions that showed a dominant DSA behavior have a higher dislocation density as compared to conditions where there was insignificant or no DSA. The dominant DSA and non-DSA tensile tested specimens had dislocation densities of 12 × 10¹⁵ m⁻² and 5 × 10¹⁵ m⁻², respectively. The shift of dominant DSA phenomena was explained with the help of dislocation waiting time at local barriers and diffusion time of solute atoms at the test temperature.