Segregation at stacking faults within the γ′ phase of two Ni-base superalloys following intermediate temperature creep

Investigation of secondary hardening in Co–35Ni–20Cr–10Mo alloy using analytical scanning transmission electron microscopy

“…Mg-Zn-Y alloys [42], Ni-Co based superalloys [43], γ′ precipitates in Ni based superalloys [44], and other members in the "MP" family of alloys [45]. The results of this study agree with aforementioned Ni-Co studies in the observation of Mo segregation, however it has been reported elsewhere both experimentally [44] and theoretically [43] that increases in Co and Cr at stacking faults occurs in addition to the changes in Mo and Ti depending on the alloy composition.…”

“…Mg-Zn-Y alloys [42], Ni-Co based superalloys [43], γ′ precipitates in Ni based superalloys [44], and other members in the "MP" family of alloys [45]. The results of this study agree with aforementioned Ni-Co studies in the observation of Mo segregation, however it has been reported elsewhere both experimentally [44] and theoretically [43] that increases in Co and Cr at stacking faults occurs in addition to the changes in Mo and Ti depending on the alloy composition. Further phase field modeling work on the specific chemistry of MP35N would be required to understand this discrepancy as the model reported by Koizumi et al [43] shows the elements that segregate to stacking faults are strongly dependent on the minor alloying additions to the material [43].…”

High resolution energy dispersive spectroscopy mapping of planar defects in L12-containing Co-base superalloys

“…Recently, creep-induced segregation along SISFs in Ni-base superalloys was observed by Viswanathan et al [22]. Various -forming elements (Co, Cr, and Mo) were observed to segregate to the SISFs, with depletion of 0 -forming elements (Ni and Al).…”

“…Recently, chemical fluctuations along SISFs that formed during creep at 750 • C in the γ phase in Ni-base superalloys CMSX-4 and ME3 were observed by Viswanathan et al [22] using the same ChemiSTEM system as outlined in Section 2. In the CMSX-4 alloy, Co and Cr were enriched at the SISF while Al and Ni were depleted.…”

“…The mechanism for local chemical fluctuations across the SISF could benefit from further diffusion investigations. Viswanathan et al [22] proposed three mechanisms for diffusion of solute to/away from the SISFs: (1) diffusion that occurs perpendicular to the fault, (2) diffusion that occurs along the fault (presumably to/from the γ matrix), and 3 wherex is the average slip distance of the leading partial dislocation, and ⇢ sp is the total Shockley superpartial dislocation density that has assisted to accommodate shearing of the 0 phase. Here the total shearing superpartial dislocation density was determined by…”