Coble creep in a powder-metallurgical nickel aluminide of composition Ni–22.8Al–0.6Hf–0.1B (at. %)

Abstract

Coble creep, which is controlled by mass transport along grain boundaries, has been identified in a powder-metallurgically prepared nickel aluminide with the nominal composition Ni–22.8Al–0.6Hf–0.1B (at. %). Diffusional creep rates∊as a function of temperatureT, stressσ, and grain sizeLare well described by∊ = 33δbDbΩσ(kTL3), whereδbDb= 3 × 10−6m3s−1× exp [– (313 kJ/mol)/(RT) (δbis the diffusional grain boundary width,Dbis the grain boundary diffusivity,Ris the gas constant, andTis the absolute temperature). The activation energy of 313 kJ/mol is unusually high as compared to that for volume diffusion.