Experimental investigation of a Portevin-Le Chatelier band in Ni-Co-based superalloys in relation to γ' precipitates at 500 °C

The macroscopically localized deformation behaviors of Ni-Co-based superalloys with different gamma' precipitate content were investigated at 500 degrees C and 1 x 10(-4) s(-1) via an in situ method namely, digital image correlation (DIC). The DIC results showed that the serrated flow of the stress-strain curves was accompanied by localized deformation of the specimens. The fracture morphology was characterized mainly by transgranular fracture with numerous dimples in the low gamma' content alloy, and intergranular fracture with large fracture section in the high gamma' content alloy. The Portevin-Le Chatelier (PLC) effect occurred in the investigated Ni-Co-based superalloys. Furthermore, the localized deformation of the high gamma' content alloy was more severe than that of the low gamma' content alloy, and the band width was slightly larger. Moreover, for the first-time ever, a special propagation feature, namely +/- 60 degrees zigzag bands characterized by head-to-tail connections, was observed in the high gamma' content alloy. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.