Investigation on the tensile deformation mechanisms in a new Ni-Fe-base superalloy HT700T at 750 °C

After a standard heat treatment and subsequent isothermal aging at 750 degrees C for 8,220 h, the tensile deformation behavior of a novel precipitation-hardened Ni-Fe-base superalloy HT700T containing around 23 vol% of gamma' precipitates is studied at 750 degrees C. It is found that the work-hardening rate decreases monotonously with plastic strain. Transmission electron microscopy observations on the specimens stretched to various magnitudes of plastic strain reveal that Orowan looping prevails at the very beginning of plastic deformation. Whereas, as plastic deformation proceeds, more and more isolated superlattice stacking faults are produced within the gamma' precipitates although numerous dislocation loops have surrounded the same gamma' precipitates, suggesting shearing of gamma' precipitates by {111} '112' slip systems plays a more and more important role in the plastic deformation with strain. Based on the experimental observations, the relationship between the operative deformation mechanisms and the work-hardening rate of HT700T is discussed. (C) 2020 Elsevier B.V. All rights reserved.