Investigation on tensile deformation and fracture behavior of a Ni-based superalloy specially designed for additive manufacturing

Abstract

A nickel-based superalloy special developed for additive manufacturing (AM) were prepared by laser directed energy deposition (LDED) technology. Through tensile test at different temperatures, the ultimate tensile strength (UTS), yield strength (YS), and elongation were obtained; The corresponding microstructure and fracture morphologies were characterized as well as the properties. The results show that the abnormal peak values of UTS and YS were found at 700 °C, accompanying with poor ductility. Furthermore, the value of flow stress is little affected by strain rate in the temperature range of 23–700 °C, while it is very sensitive for that of 800–1100 °C. The dominant deformation mechanism of the former is anti-phase boundary (APB) shearing, and the fracture is featured by shear fracture without obvious necking; while for the latter, the dislocation climbing, cross-slip and Orowan looping is dominant, and the fracture mechanism is mainly characterized by the aggregation and growth of micropores and crack propagation, and postmortem specimen exhibit distinct necking phenomena. The abnormal peak values of UTS and YS at 700 °C could be attributed to the formation of Kear–Wilsdorf locks (K-W locks). The experimental results will support the application of the investigated alloy as well as design new alloy for AM.