Interfacial segregation and influence of antiphase boundaries on rafting in a γ/γ′ alloy

Abstract

An interface consisting of an antiphase boundary (APB) and a short-range-ordering interphase layer (ϳ4 nm) in the elongated ␥Ј precipitate for a chosen model alloy was examined. Interface image simulations, high-resolution electron microscopy (HREM), and scanning transmission electron microscopy (STEM) techniques were employed to show interfacial segregation at an APB and to identify the local composition changes across it. Emphasis is also given to understanding the influence of the APB on the microstructural evolution in the rafting mechanism. In contrast to the widely accepted notion that out-of-phase precipitates never coalesce to form a single particle, results of this study indicate that complete coalescence of ␥Ј precipitates during annealing may occur at high temperatures as a result of the glide and climb of a 1/2 Ͻ110Ͼ superpartial dislocation in the thin interphase layer, despite the presence of an APB between the merging ␥Ј particles.

Temperature dependence of the pre-wetting transition at the (1 1 1) anti-phase boundary in Ni3Al: an atomistic study

“…The Ni enrichment of (1 1 1) APBs is consistent with the crystal symmetry analysis for the L1 2 -structure performed by Braun et al [16]. It is also in agreement with direct experimental observations [17]. Note that the minimum on the profiles deepens with decreasing temperature.…”

“…The atomistic simulations reported in this work predict that the (1 1 1) APB in the γ phase of the Ni-Al system undergoes significant structural and compositional changes with varying temperature and the bulk composition c γ . Ni atoms segregate to this APB at all temperatures and bulk compositions studied in this work, which is consistent with experiment [17]. As Ni concentration in the bulk increases at a fixed temperature, the APB region enriched in Ni widens and can reach 1 to 1.5 nm in thickness, depending on the temperature.…”

Coupling phase field and viscoplasticity to study rafting in Ni-based superalloys

“…Note that, in most cases, the neighboring γ domains are in antiphase relationship and will thus never coalesce to form a single domain. However, in experiments, two γ domains initially in antiphase relationship may coalesce in the presence of plastic activity [74]. Indeed, when a dislocation of the matrix (whose Burgers vector b is of the type 1/2[110]) crosses the channel delimited by the two γ domains, the relative position of the two γ domains is shifted by b.…”

Kinetics of rafting in a single crystal superalloy: Effects of residual microsegregation

“…Rafting is most commonly observed in high temperature creep tests, [3][4][5][6] but even nowadays its effect on creep performance remains both contradictory 7,8 and sometimes controversial. 9 However, it should be noted that it is now well established that rafting can proceed even in the absence of applied load, provided that a critical amount of plastic strain has already been induced and provided that the temperature is sufficiently high.…”