Atomic structure and elemental segregation behavior of creep defects in a Co-Al-W-based single crystal superalloys under high temperature and low stress

L12‐Strengthened Co‐Rich Alloys for High‐Temperature Structural Applications: A Critical Review

“…[ 85 ] The mode of the γ′ shearing is expected to be governed by the energy differences between the APB and SISF, [ 3 ] whereas both the APB energy and the SISF energy are dependent on the alloy compositions and deformation temperatures. In addition, solute segregation to planar and linear faults has also been reported recently via high‐resolution scanning transmission electron microscopy and atom probe analyses, [ 89,90 ] together with associated microstructural evolutions and localized phase transformations, all of which are believed to have a profound influence on their high‐temperature mechanical properties. [ 91,92 ] Therefore, to further optimize the Co‐rich multicomponent alloys for high‐temperature application, a more integrated understanding of the intrinsic factors controlling the creep and fatigue performances under various temperatures and external stress levels is still needed.…”

Influence of the γ′ Volume Fraction on the High-Temperature Strength of Single Crystalline Co–Al–W–Ta Superalloys

“…In contrast, at higher stresses such as 350 MPa, shearing of γ precipitates readily happened in VF60 within a shorter time than at lower stresses, leading to a limited contribution of strengthening by rafting and the formation of a single creep rate minimum. In the case of VF70, its higher γ volume fraction of 81% than that of VF60 with 70% may have enabled more plastic deformation in the γ precipitates and a higher chance of SF interaction for hardening [31,33].…”

“…At a lower γ volume fraction of 55%, the highest creep strength was reached at high temperature and low stress, where rafting reduced the size of the vertical γ channels and the corresponding dislocation climbing along them [25]. Unlike in Ni-based superalloys, the deformation was mainly dominated by the shearing of γ precipitates under the formation of planar faults, such as anti-phase boundaries and stacking faults in Co-and CoNi-based superalloys because of their low stacking fault energy [2,[26][27][28][29][30][31][32][33]. It has further been found that increasing the γ volume fraction up to 80-90% can lead to even higher YS [16] and creep strength [20,34] in these superalloys.…”

Enhanced creep performance in a polycrystalline superalloy driven by atomic-scale phase transformation along planar faults

“…For instance, Co and Cr have been found to segregate preferentially onto partial dislocations along with Re and Mo [14][15][16][17][18]. Segregation at other crystal defects such as APBs, SISFs and SESFs in the γ' precipitates has also been observed [19][20][21][22][23]. In some cases, depending on the level of alloying, these interactions can induce local ordering and result in a phase transformation, such as the formation of ordered, hexagonally-closed-packed (hcp) structured χ and η phases along SISF and SESF, respectively, in some experimental highrefractory content Ni-based superalloys [17,21,24,25].…”

“…Super Energy dispersive X-ray spectrometry (EDX)transmission electron microscopy (TEM) has been extensively used providing structural and compositional information from integrated signal through the thickness of the TEM specimen [13,[19][20][21][22][23][24]. More recently, correlative atom probe tomography (APT) and TEM analyses in CoNi-based superalloys have proven to be very efficient to characterize the partitioning of solutes at crystal defects, with near-atomic level quantification of the local compositions [16,17,26].…”