DIFFUSIVITIES AND ATOMIC MOBILITIES IN FCC AG-CU-MG-MN ALLOYS

Ag-based alloys with existence of face-centered cubic (fee) phase have been found to possess high electrical and thermal conductivity, low light absorption. It was reported that addition of Cu, Mg and Mn in Ag-based alloys can increase the strength and resistivity and improve charge mobility of the alloys but decrease its electrical and thermal conductivity [1]. From both practical and scientific points of view, diffusion has attracted much interest in recent years for their applications in multi- component alloy designs. Recently, the diffusion controlled transformation (DICTRA) software program [2], which is operated under the CALPHAD framework has been wildly utilized to study the diffusion behavior in material and predict microstructural evolution. Such a method is focusing on the development of atomic mobilities of target alloys which are then combined with corresponding thermodynamic database to obtain diffusivities that are indispensable for computational kinetic studies. On the basis of Ag/Ag-Mg and Ag/Ag-Mn semi-infinite diffusion couples, the interdiffusion coefficients in fee phase of the Ag-Mg, and Ag-Mn alloys were measured at the temperature ranges between 873 and 1173 K by using the Sauer-Freise method [3]. Furthermore, by employing groups of bulk diffusion couples together with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Ag-rich fee Ag-Mg-Mn, Ag-Cu-Mn and Ag-Mg-Cu alloys at 873, 973 and 1073 K were determined via the Whittle and Green method. The experimental interdiffusion coefficients were critically assessed to obtain the atomic mobilities of Ag, Cu and Mg and Mn in fee Ag-Mg, Ag-Mn, Ag-Mg-Mn, Ag-Cu-Mn and Ag-Mg-Cu alloys by using the DICTRA (Diffusion Controlled TRAnsformations) software package. Finally, the experimental concentration profile in Ag-Cu-Mg-Mn quaternary alloys can be simulated based on available thermodynamic information and obtained mobilities for the fee Ag-Mg, Ag-Mn, Ag-Mg-Mn, Ag-Cu-Mn and Ag-Mg-Cu systems. Moreover, the simulated results agree in general with experimental data. This work contributes to the establishment of a Ag-based kinetic database for computational design of high thermal and high electrical conductivity silver alloys.