On the role of topological inversion and dislocation structures during tertiary creep at elevated temperatures for a Ni-based single crystal superalloy

Abstract

Abstract Creep behaviors of a 3rd generation single crystal superalloy DD33 at 1100 °C/1120 °C/1150 °C and 120 MPa have been characterized. The role of topological inversion and dislocation structures during tertiary creep have been studied. It is found that the tertiary duration is inversely related to the creep temperature. The higher the temperature is, the faster the tertiary creep rate rises and the higher the maximum rate is. The topological inversion level also shows a negative correlation with the temperature and the γ/γʹ inversion cannot account for the rapid increase in the tertiary rate. The formation of γʹ-junctions and the diffusion of γ/γʹ-forming elements result in the phase inversion, which strongly depends on the tertiary duration. Moreover, with the temperature increases from 1100 °C to 1150 °C, the main mobile dislocations are the long straight a superdislocations, the individual screw a superdislocations and the interface-deposited 60° dislocations, respectively. The factors affecting the tertiary creep rate have been analyzed in detail.