Differential scanning calorimetry analyses of Al-Cu-Zn alloys

LM2S, Physics Department, Faculty of Science, Badji-Mokhtar University, PB 12, Annaba 23000, Algeria

^a e-mail: draissia@yahoo.fr

Received: 4 March 2012
Revised: 1 August 2012
Accepted: 6 August 2012
Published online: 1 October 2012

Abstract

The effect of heat treatment on phase transformation and crystalline microstructure properties of ternary Al-Cu-Zn alloys made under nonequilibrium conditions was investigated by means of differential scanning calorimetry spectrometry (DSC), optical microscopy observations and X-ray diffraction (XRD) patterns analyses. A set of ternary Al-X wt.% Cu-X wt.%Zn alloys with nominal compositions X = 2, 8, 20 and 25 were rapidly solidified under vacuum by high-frequency magnetic induction melting process. It was found that DSC heating at temperatures below 500 °C leads to phase transformation with the development of new phases which were identified by XRD patterns analyses such as the presence at ambient temperature of the rhomboedric structure τ′-Al₄Cu₃Zn phase in equilibrium with the expected tetragonal θ-CuAl₂ in Al matrix. Measured DSC crystallization enthalpies of occurring phase transformation were given. Optical microscopy observations reveal refined grains and homogeneous surface textures of the as-melted Al-Cu-Zn alloys.