COMPUTER-SIMULATION OF PHASE-DECOMPOSITION OF AL-ZN ALLOY BASED UPON NONLINEAR DIFFUSION EQUATION

Computer simulation of phase decomposition was performed for the G. P. zones of Al-Zn alloy system on the basis of the Cahn-Hilliard's non-linear diffusion equation. In the calculation, the modified regular solution approximation was adopted, i.e. the composition and temperature dependences of the interaction parameter OMEGA. between the nearest neighbor atoms were taken into account and the mobility of the system was defined as a function of solute composition. Al-Zn alloy systems have asymmetry concerns with the solute composition on phase diagram, that is different from the alloy systems calculated in the previous papers where regular solution model and Cu-Co alloys. The phase decomposition was successfully computed for the G. P. zones of Al-Zn alloy. The calculation method is applicable for the alloys, whose decomposition regions have asymmetry with solute composition. It is expected that the simulation is useful in the analysis of phase decomposition process.