Grain boundary diffusion and segregation of Bi in Cu: radiotracer measurements in B and C diffusion regimes

Grain boundary (GB) radiotracer diffusion of {sup 207}Bi in polycrystalline Cu was measured in Harrison's B (1198-843 K) and C (659-536 K) kinetic regimes. In the B regime the triple product P=s{center_dot}{delta}{center_dot}D{sub gb} (where s is the segregation factor and {delta} the GB width) was found to obey the Arrhenius law P=6.6x10{sup -12}xexp (-102.8 kJ mol{sup -1}/RT) m{sup 3} s{sup -1}. The measurements in the C regime yielded the temperature dependence of the Bi GB diffusion coefficient D{sub gb} in Cu, D{sub gb}=0.24xexp (-156.2 kJ mol{sup -1}/RT) m{sup 2} s{sup -1}. Assuming that {delta} congruent with 5x10{sup -10} m the segregation factor s of Bi in Cu was determined in the limit of very dilute solute concentration to follow an Arrhenius dependence s=s{sub 0}exp(-{delta}H{sub s}/RT) with the pre-exponential factor s{sub 0}=0.054 and the segregation enthalpy {delta}H{sub s}=-53.4 kJ mol{sup -1}.