ESTIMATION OF ARRHENIUS PARAMETERS OF GRAIN-BOUNDARY CHEMICAL DIFFUSION OF SN IN A PB-9.87 AT.PERCENT SN ALLOY THROUGH KINETIC-ANALYSIS OF DISCONTINUOUS PRECIPITATION

The present investigation concerns a systematic kinetic analysis of di scontinuous precipitation (DP) in a Pb-9.87 at.% Sn alloy. The study i ncludes a quantitative estimation of the Arrhenius parameters of grain boundary chemical diffusion of Sn in this alloy in the temperature ra nge 258 to 333 K using the Petermann-Hornbogen model for DP. In the co urse of DP under isothermal condition, the reaction front migrates wit h a steady-state velocity, upsilon, and the interprecipitate repeat di stance, lambda, remains statistically constant. The variation of upsil on and lambda with temperature has been determined. Finally, the DP re action in this alloy seems to be a boundary diffusion controlled proce ss, the activation energy of which lies in between 39.8 and 42.2 kJ/mo l.