The Dependence of Portevin–Le Châtelier Effect on the γ′ Precipitates in a Wrought Ni-Base Superalloy

Abstract

The dependence of Portevin–Le Châtelier (PLC) effect on the γ′ precipitates of the Nimonic 263 alloy in different microstructural conditions has been studied by analyzing the parameters of the tensile curves and the deformation mechanisms. It is shown that the γ′ precipitates with different sizes, edge-to-edge interprecipitate distance, and areal number density are obtained by altering the aging time. It is demonstrated that when the mean size of the γ′ precipitates is less than 28 nm (aging less than 25 hours), the deformation mechanisms are dominated by APB-coupled a/2〈101〉 dislocations shearing the small γ′ precipitates and the slip bands continuously cutting the γ and γ′ phases. When the γ′ size is between 28 and 45 nm (aging time between 25 and 50 hours), the deformation mechanism is controlled by the APB-coupled a/2〈101〉 dislocations shearing the small γ′ precipitates, the a/6〈112〉 Shockley partial dislocation continuously shearing the γ and γ′ phases combined with matrix dislocations by-passing the γ′ precipitates; If the γ′ size over 45 nm (aging time more than 50 hours), Orowan by-passing becomes the main deformation mechanism. Moreover, with increasing the aging time, the critical plastic strain for the onset of the PLC effect increases and reaches a maximum after aging for 50 hours, and then gradually decreases. At last, the dependence of critical plastic strain on the deformation mechanisms is well explained by the elementary incremental strain (γ). The precipitation process of the γ′ phase can directly influence the PLC effect by changing the interactions among solutes atoms, mobile dislocations, and forest dislocations.