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

TL;DR

This study investigates the formation and thermodynamic properties of the eta' phase in an AlZnMgCu alloy produced by mechanical alloying, revealing how heating rates influence phase behavior and energy barriers.

Contribution

It introduces a novel analysis of the eta' phase's thermodynamic parameters in mechanically alloyed AlZnMgCu alloy, highlighting the effect of heating rate on phase transformation.

Findings

Eta' phase forms after 40 hours of mechanical alloying.

Thermodynamic barriers vary significantly with heating rate.

Activation energies align with diffusion energies of alloying elements.

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.