Search

Here, we investigate a new type of kink structure that is found at γ/γ′ interfaces in nickel-based single crystal superalloys. We studied these structures at the atomic and elemental level using aberration corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The core of the dislocation absorbs high-Z elements (i.e., Co and Re) that adopt hexagonal arrangements, and it extrudes elements (i.e., Ni and Al) that adopt face centered cubic (fcc) structures. High-Z elements (i.e., Ta and W) and Cr, which is a low-Z element, are stabilized in body centered cubic (bcc) arrangements; Cr tends to behave like Re. High-Z elements, which migrate and adopt a hexagonal structure, induce kink formation at γ/γ′ interfaces. This process must be analyzed to fully understand the kinetics and dynamics of creep in nickel-based single crystal superalloys. [ABSTRACT FROM AUTHOR]

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 ( 1 1 ¯ 1 ) half plane and one ( 11 1 ¯ ) half plane. This dislocation was decomposed into two partial dislocations b 1 and b 2 , with b 1  = a/2 [ 1 ¯ 01 ] and b 2  = a/2 [ 1 ¯ 10 ] . Partial dislocations b 1 and b 2 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. [ABSTRACT FROM AUTHOR]