Investigation of room temperature strengthening mechanism on PM Ni-base superalloys with tantalum addition

Abstract

In this paper, the mechanical properties of the high-performance powder metallurgy (PM) superalloys with Ta addition fabricated by the Central Iron and Steel Research Institute (CISRI) were evaluated at room temperature (RT). We focus on the reason why the solute element Ta affects RT properties of PM superalloys. To this end, the necessary advanced characterization methods were used to study the plastic deformation and fracture mechanisms. The results revealed that the leading cause for the enhancement in RT yield strength with Ta increasing is the antiphase boundary (APB) strengthening of the bimodal γ' precipitates, the extended stacking fault (ESF) shear and the interaction between ESF and dislocation. Importantly, the microtwin structure was found in the deformed substructure, which is an extraordinary phenomenon in RT plastic deformation for PM superalloys. • The microtwin configuration was found inL1 2 -γ' strengthening Ni-base PM superalloys after RT tensile defromation. • The microtwins are formed by the a/6 〈112〉Shockley partials shearing precipitates on adjacent {111} planes. • The deformation induced ESFs (or microtwins) is the major reason for the increase in yield strength.