Influence of microtwins on Portevin-Le Chatelier effect of a Ni-Co based disk superalloy

Influence of microtwins (MTs) on Portevin-Le Chatelier (PLC) effect of a Ni-Co-based superalloy was investigated by tensile tests and transmission electron microscopy. Two groups of samples were pre-strained at 725 degrees C to produce MTs. Existence of MTs improved the alloy's yield strength, but it changed the PLC effect from type-B to type-C, and increased the serration amplitudes by similar to 6 times, during tensile deformation at 400 degrees C. Microstructural characterizations indicate that dislocation-MT interactions lead to break of MTs in both gamma matrix and gamma' precipitates, creating soft channels for dislocation glide. The high serration amplitudes were rationalized on the basis of sudden plastic flow along those soft channels and subsequently strain hardening due to dislocation multiplication. These results demonstrate that MTs influence the PLC effect much more significantly, compared with traditionally accepted dislocation-solute interactions. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The presence of MTs increased the alloy's yield strength but changed the PLC effect type and increased serration amplitudes significantly. The interaction between dislocations and MTs created soft channels for dislocation glide, resulting in high serration amplitudes during deformation.