Impact of the twin boundary on nickel-based superalloy behavior during tensile deformation using molecular dynamics

Abstract

The improvement of nickel-based superalloys' mechanical properties can be achieved by controlling the grain boundary structure, particularly the twin boundary. Understanding the role of the twin boundary in deformation and mechanical properties can develop grain boundary engineering strategies to increase the mechanical properties of nickel-based superalloys. This paper examines the effects of three different orientations of the twin boundary to the loading direction, i.e., parallel, inclined, and perpendicular under uniaxial tensile loading, on the mechanical properties and mechanisms of slip and dislocation generation. A molecular dynamics model is used to simulate the behavior of the nickel-based superalloy. The results indicate that the yield stress of the nickel-based superalloy is improved by the twin boundary perpendicular to the loading direction. In contrast, parallel and inclined twin boundaries weaken the material's yield stress. The yield stresses are 12.97, 11.45, 10.33, and 13.65 GPa, respectively, for the sample without a twin boundary, containing a twin boundary parallel, inclined, and perpendicular to the loading direction. The results demonstrate that when the twin boundary is parallel or perpendicular to the loading direction, the slip planes are inclined to the twin boundary. However, when the twin boundary is inclined to the loading direction, the dislocations mainly slip gradually parallel to the twin boundary. Also, the twin boundary changes the material's toughness. The toughness values for samples without the twin boundary and with the twin boundary parallel, inclined, and perpendicular to the loading direction are 0.134, 0.139, 0.292, and 0.06 GPa, respectively. Also, the creation and growth of the crack due to the ultimate stress occurs at points in the phase interface for the parallel twin boundary and in the twin boundary for the inclined and perpendicular twin boundaries.