Grain boundary diffusion and segregation of Ni in Cu

Grain boundary (GB) diffusion of 63Ni in polycrystalline Cu was investigated by the radiotracer technique in an extended temperature interval from 476 to 1156 K. The independent measurements in Harrison’s C and B kinetic regimes resulted in direct data of the GB diffusivity Dgb and of the so-called triple product P = s · δ · Dgb (s and δ are the segregation factor and the diffusional GB width, respectively). Arrhenius-type temperature dependencies for both the Dgb and P   values were measured, resulting in the pre-exponential factors Dgb0=6.93×10-7 m2 s−1 and P0 = 1.89 × 10−16 m3 s−1 and the activation enthalpies of 90.4 and 73.8 kJ mol−1, respectively. Although Ni is completely soluble in Cu, it reveals a distinct but still moderate ability to segregate copper GBs with a segregation enthalpy of about −17 kJ mol−1.