Metallurgical Abstracts on Light Metals and Alloys vol.56
Investigation of the role of Sn on negative effect in two-step aging in an Al-Mg-Si alloy by XAFS analysis
Serina Tanaka* and Hiroki Adachi**
* Graduate student, Graduate School of Engineering, University of Hyogo
** Graduate School of Engineering, University of Hyogo
[Published in Journal of The Japan Institute of Light Metals, Vol. 72, No. 10 (2022), 593-599]
https://www.jstage.jst.go.jp/article/jilm/72/10/72_721002/_article/-char/en
E-mail: em20X001[at]steng.u-hyogo.ac.jp
Key Words: Al-Mg-Si alloy; cluster; XAFS
The effect of Sn addition on clustering behavior of natural aging (NA) in Al-0.95mass%Si-0.56mass%Mg-0.04mass%Sn alloys was studied via X-ray absorption fine structure (XAFS) measurements and first-principles calculation. XAFS measurements near the Sn-K edges were taken at BL14B2 beamline, near the Si-K and Mg-K edges were taken at BL27SU beamline at SPring-8. Density functional theory (DFT) calculations were used to determine the valence electron densities near Sn atoms. Sn-K XANES measurements showed that the absorption edge energy near Sn-K edge shifted 0.6eV to the lower energy side for NA times from 0.6ks to 36ks. Therefore, it was found that the bonding ratio of Sn to vacancy gradually increases for NA 36ks, while Sn atoms were not actively included in clusters composed of Mg and Si atoms. In addition, compared the hardness measurements results with XAFS measurements and first-principles calculation results, it is suggested that the formation of Mg-vacancy pairs is delayed by the binding of Sn atoms to vacancy, which delays the participation of Mg-vacancy pairs in the cluster, thus the formation of clusters is delayed.
Fig.(a) shows XANES spectra near Sn-K edge of Sn added Al-Mg-Si alloys and Fig.(b) shows the enlarged view of the area enclosed by the red dotted line in Fig.(a). For NA times from 0.6ks to 36ks, the absorption edge energy shifted 0.6eV to the lower energy side.