امين قائدرحمتي

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 to 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 to 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. Hence, the inverse PLC effect was observed at 750 °C in the sample which had rolled at 1150 °C. Whilst the serrated flow was not seen at 750 °C in the samples which had rolled at 950 °C and 1050°C. The critical strain, for the initiation of the serrated flow was found to reduce with the increasing temperature of hot rolling from 950 °C to 1150 °C. After tensile test, the microstructural eva‎luations revealed the proven substantial role of the precipitation of Cr-rich M23C6 carbides in pinning of the mobile dislocations, which led to the inverse PLC effect.

پيركرنشي ديناميكي , نورد گرم , عمليات ترمومكانيكي , اينكونل 617 , ريزساختار , جريان دندانه‌دار

Dynamic strain aging , Hot rolling , Thermomechanical processing , Inconel 617 , Microstructure , Serrated flow

Amin Ghaedrahmati

Dr. Hamid Reza Jafarian Dr. Ali Reza Eivani