Thermodynamic parameters of the eta' phase in an AlZnMgCu alloy synthesized by mechanical alloying

Abstract

We synthezised an AlZnMgCu alloy through mechanical alloying and, using Xray diffraction (XRD), identified the formation of the eta prime phase after 40 hours of grinding. Using reaction-free isoconversion theory, we determined that this phase exhibits two different behaviours depending on the heating rate (beta): the eta prime phase at low beta and the eta phase at high beta.The activation energy values at low beta are consistent with the diffusion energies of copper, zinc and magnesium in aluminium. Significant qualitative and quantitative differences in the thermodynamic barriers (Delta H, Delta G and Delta S) are observed for beta values above or below 20 deg C min minus 1.