EFFECT OF SEGREGATION ON THE SHAPE OF GRAIN-BOUNDARY DIFFUSION PROFILES EXPERIMENTAL-STUDY OF THE CU-AG SYSTEM

Grain boundary diffusion of Ag in Cu and in a Cu-0.091 at.% Ag alloy h as been investigated. An experimental method to separate the effect of different grain boundaries present in the samples and the effect of s egregation on grain boundary diffusion profiles is described. It is sh own that in the case of silver diffusion in pure copper the curved pen etration plots are due to segregation effects. For pure Cu the obtaine d activation energy and pre-exponential factor of the triple product P are (90 +/- 6.2) kJ mol(-1) and (3.7(-2.5)(+7.3)) x 10(-14) m(3) s(-1 ) respectively. For Cu(Ag) alloy these values are (119.4 +/- 6.6) kJ m ol(-1) and (2.1(-1.5)(+4.8)) x 10(-12) m(3) s(-1), respectively. The a ctivation energy of grain boundary segregation is estimated as 37 +/- 13 kJ mol(-1).