Portevin-Le Chatelier effect in a wrought Ni-Co based superalloy

For investigating the Portevin-Le Chatelier (PLC) effect in a wrought Ni-Co based superalloy with low stacking fault energy, the tensile tests of Ni-30%Co based superalloy within the temperature range of 350-550 degrees C and strain rate range of 3 x 10(-5) -3 x 10(-3) s(-1) were carried out. The microstructures were observed by optical microscope (OM) and transmission electron microscope (TEM). The serrated flow of stress-strain curves exhibited various characteristics based on the deformation conditions. The serrations transformed from type-A to type-C with increasing temperature or decreasing strain rate. The normal and inverse PLC effects were analyzed based on unpinning and pinning of mobile dislocations. The microstructural evolution shown that the deformation mechanisms were dislocation slip and stacking fault. Additionally, the tests of sample with large high-density stacking faults revealed that the amplitude of stress drop was determined by strength of the solute and microtwin obstacles. (C) 2019 Elsevier B.V. All rights reserved.