The low cycle fatigue deformation response of a single-crystal superalloy at 650 °C

Abstract

The purpose of this study was to characterize the cyclic stress-strain response, the corresponding deformation structure and their relationships in the single crystal nickel-base superalloy PWA 1480. The isothermal low cycle fatigue response and deformation structures of specimens oriented near the [001], [2 5 20], [3 6 10], [011], [234] and [111] crystallographic orientations were characterized at an intermediate temperature (650 °C). The initial yield strength of all these specimens was controlled by the shearing of the γ′ precipitates by dislocation pairs. The low cycle fatigue tests exhibited cyclic hardening, which was associated with dislocation interactions in the γ matrix. In specimens deforming by slip on a single slip system, dislocations of the primary slip system accumulated in the γ matrix and formed sessile entanglements. In specimens deforming by slip on several slip systems, the dislocations of the different operative slip systems intersected in the γ matrix and formed sessile arrangements.