Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

Abstract—The results of the density functional theory calculation of the segregation energy of refractory metals at grain boundaries (GBs) in the alloys based on nickel (fcc solid solutions), chromium (bcc), and titanium (hcp) are analyzed. The influence of segregation on the cohesive strength of GBs is estimated using the Rice–Wong model, in which the mechanical strength of GBs is characterized by the boundary splitting energy. Refractory metals are shown to contain “useful” elements, which enrich GBs and increase their cohesive strength in alloys of all types. The calculated data are used to design experimental high-temperature alloys (HTAs), the alloying system of which contains useful elements in the form of a package of low-alloy additives in HTAs, namely, nickel (Zr, Nb, Hf, Ta), chromium-based (Nb, Ta), and titanium (W, Ta, Re) alloys. The results of testing the mechanical properties of these experimental alloys are presented. The low-alloy additives are shown to increase the creep resistance of all alloys at elevated temperatures.