Grain boundary radiotracer diffusion of71Ge and72Ga in Al and Al–Ga alloys

Abstract Grain boundary (GB) solute diffusion of Ge and Ga in Al polycrystals was investigated by the radiotracer serial sectioning technique using 71Ge and 72Ga isotopes. The diffusion measurements were carried out under conditions of Harrison's B-kinetics regime in the temperature range 450–680 K. The measured triple products P = sδDgb (s is the segregation factor, δ the GB width and Dgb the GB diffusivity) were found to follow the Arrhenius law with pre-exponential factors and activation enthalpies of 6.36 × 10−14 (5.33 × 10−13) m3/s and 53.6 (54.8) kJ/mol for Ge (Ga), respectively. Alloying of Al by Ga results in a slight increase of the Ge GB diffusivity by a factor of two to three at 576 K within the total Ga content up to 1 at.%. This result does not confirm the appearance of a liquid-like GB layer in the Al–Ga alloys studied.