Effect of rolling temperature on the occurrence of dynamic strain aging of Inconel 617 superalloy

Abstract

Inconel 617 specimens were hot rolled at 950 °C, 1050 °C, and 1150 °C to examine the effect of thermomechanical processing on the occurrence of dynamic strain aging (DSA), followed by performing the tensile tests at temperature range of 350 °C–750 °C with the strain rates of 5 × 10−4 s−1, 5 × 10−3 s−1, and 1 × 10−2 s−1. The microstructural evolution was studied by an optical microscope, a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). The stress-strain curves were analyzed in terms of serration intensity and types. The serrated flow at temperature range of 450 °C–750 °C underwent changes by the strain rate and the temperature, and the serration type changed from types A + B and B to type C. The transformation of Portevin-Le Chatelier (PLC) effect from normal to the inverse PLC effect was observed at a temperature higher than 550 °C. The activation energy was calculated and it was found that the diffusion of Cr and Mo substitutional atoms are mainly responsible for the DSA effect in hot rolled Inconel 617 superalloy. The hot rolling temperature was also found to have a significant impact on the occurrence of DSA. Moreover, it was indicated that as the hot rolling temperature increases from 950 °C to 1150 °C, the occurrence of dynamic strain aging is intensified.