Soft X-ray XAFS studies on Al-Mg-Si alloys with different aging conditions

Abstract

In Al-Mg-Si alloys, the negative effect for the artificial age-hardenability occurs by the cluster (1) formation during natural aging following solution treatment and the positive effect occurs by the cluster (2) formation. For the purpose of obtaining information on the constituent elements of these clusters, soft X-ray absorption fine structure (XAFS) measurements of Mg-K edge and Si-K edge were carried out with the liquid nitrogen cooling. From radial structure function calculated from the extended X-ray absorption fine structure (EXAFS) spectra, since average nearest neighbor distance from Mg atom or Si atom decreases by the formation of cluster (1), it is considered that cluster (1) contains both Mg and Si atoms. The absorption edge energy of Si-K shifted to higher energy by the formation of cluster (1). This indicates that the Si valence increased and ion binding property is high for the bonding with neighbor atoms of Si atom in cluster (1). Since the binding force of ionic bond is stronger than that of a metallic bond, cluster (1) is difficult to be decomposed in the artificial aging and the negative effect is shown.