Core structure and strengthening mechanism of the misfit dislocation in nickel-based superalloys during high-temperature and low-stress creep

Misfit dislocation structures are investigated in a nickel-based single crystal superalloy subjected to 38.8 h creep at 1100 °C and 130 MPa using conventional and high resolution transmission electron microscopy (HRTEM). The misfit dislocation was identified as an uncommon one with Burgers vector b = a/2 [2¯11], which can be described as inserting (or extracting) one (11¯1) half plane and one (111¯) half plane. This dislocation was decomposed into two partial dislocations b₁ and b₂, with b₁ = a/2[1¯01] and b₂ = a/2[1¯10]. Partial dislocations b₁ and b₂ were arranged in a “V” shape, connected by the antiphase boundary (APB), which could hinder the dislocation motion to achieve the effect of dislocation enhancement.