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Cast and wrought Ni‐based superalloys are materials of choice for harsh high‐temperature environments of aircraft engines and gas turbines. Their compositional complexity requires sophisticated thermo‐mechanical processing. A typical microstructure consists of a polycrystalline γ‐matrix, strengthening Ni3(Al,Ti) γ′ precipitates, carbides (MC, M6C, and M23C6), borides (M2B, M3B2, and M5B3), and other inclusions. Microalloying additions of B, C, and Zr commonly improve high‐temperature strength and creep resistance, although excessive additions are detrimental. Grain boundary (GB) segregation may improve cohesion and displace embrittling impurities. Finely dispersed carbides and borides are desired to control grain size via GB pinning. However, excessive decoration of GBs may lead to failure during processing and in‐service. Hence, a systematic review on the roles of B, C, and Zr in cast and wrought Ni‐based superalloys is required. The current state of knowledge on GB segregation and precipitation is reviewed. Experimental and modeling results are compared across various processing steps. The impact of GB precipitation on mechanical properties is most well researched. Co‐precipitation in proximity to GBs interacting with local microstructure evolution and mechanical properties remains less explored. Addressing these gaps in knowledge allows a more complete understanding of processing–microstructure–properties relationships in advanced cast and wrought Ni‐based superalloys. [ABSTRACT FROM AUTHOR]

Plasma focused ion beam microscopy (PFIB) is a recent nanofabrication technique that is suitable for site-specific atom probe sample preparation. Higher milling rates and fewer artifacts make it superior to Ga+ FIBs for the preparation of samples where large volumes of material must be removed, for example, when trying to avoid lift-out techniques. Transmission Kikuchi diffraction (TKD) is a method that has facilitated phase identification and crystallographic measurements in such electron transparent samples. We propose a procedure for preparing atom probe tomography (APT) tips from mechanically prepared ribbons by using PFIB. This is highly suitable for the preparation of atom probe tips of interfaces such as interphase boundaries from challenging materials where lift-out tips easily fracture. Our method, in combination with TKD, allows the positioning of regions of interest such as interfaces close to the apex of the tip. We showcase the efficacy of the proposed method in a case study on Alloy 718, where the interface between γ-matrix and δ-phase has not been yet extensively explored through APT due to preparation challenges. Results show depletion of γ″-precipitates near the γ/δ interface. A quantitative evaluation of the composition of phases in the bulk versus near the interface is achieved.