Application of effective potential formalism to mechanical alloying in Ag-Cu and Cu-Fe systems

We have used the competing dynamics model and the effective potential forma lism for studying phase stability during mechanical milling of Ag-Cu and Cu -Fe systems. We first present a method for extracting an effective potentia l for systems in which the atomic mobility may depend on alloy composition. Using an estimate for the typical ballistic diffusivity, we apply this for malism to calculate the dynamical phase diagram for the Ag-Cu and Cu-Fe bin ary systems under mechanical milling. For the Ag-Cu system, the dynamical p hase diagram exhibits a miscibility gap that closes in on itself at low tem peratures, due to the exponentially decreasing thermal diffusivity land hen ce, increasing influence of ballistic diffusivity) with decreasing temperat ure. In the Cu-Fe system, in which the effective potential for both the bce and fee phases need to be taken into account, the fee phase is shown to be stabilized at low temperatures for all the alloys, except the almost pure iron (which is stabilized in its bce form). These results are critically co mpared with available experimental results. (C) 2001 Elsevier Science B.V. All rights reserved.