Metallurgical Abstracts on Light Metals and Alloys vol.57

Inﬂuence of Heat Treatment Time on Oxide Scale Formed on Mg Containing Al Based Alloys

Atsushi Jo*, Masaaki Kato** and Akira Yamauchi**
* Advanced Engineering Course Student, Department of Production Systems Engineering, National Institute of Technology, Gunma College
** Department of Mechanical Engineering, National Institute of Technology, Gunma College

[Published in Journal of The Japan Institute of Light Metals, Vol. 74 (2024), pp. 147-152]

https://www.jstage.jst.go.jp/article/jilm/74/3/74_740309/_article/-char/en
E-mail: ayama[at]gunma-ct.ac.jp
Key Words: Heat treatment; Al-Mg alloy; AC4B; Oxide scale; MgAl₂O₄

Cube specimens of AC4B aluminum alloy, Al-1%Mg, and Al-3%Mg were oxidized in air at 773 K for up to 25 h to investigate the inﬂuence of heat treatment time and Mg concentration. The original specimens and oxidation products were characterized by X-ray diffractometry, scanning electron microscopy, and X-ray photoelectron spectroscopy. SEM observation showed that the oxide scale grew thick and the surface of the oxide scale consisted of granular grain. Simultaneously, the tone color of the specimens became darker. The XRD and XPS analysis indicated that oxide scales mainly consist of MgO and MgAl₂O₄, and the top surface was covered with MgO. In addition, the ratio of MgAl₂O₄ on the surface of oxide scales tended to increase with heat treatment time. The XPS depth proﬁle of Al-3%Mg alloy showed that oxide scale grew up to the thickness of 6 µm. The thermodynamic calculations suggested that the most stable compound on the surface of specimens is MgAl₂O₄ and then the kinetic factor is strongly inﬂuenced by the surface oxidation of Mg-containing Al alloys.

Cross-sectional SEM images and EPMA mapping of oxide scale formed on Al-3%Mg alloys and AC4B at 773 K for 25 h in an air.