B22-P-07Structural Analysis of Au Doped Titanium Disilicide using Cs-corrected Scanning Transmission Electron Microscopy

Al-Mg-Si-based alloys are widely used and studied due to the increasing demand of reducing weight of automobile body panels. One of the main topics in the studies is improvement of the hardening response in the initial stage of artificial aging. Recently, Koshino et al. reported that 0.04 wt.% addition of Li increases the hardness of an Al-Mg-Si alloy aged for not only 10 hours (peak aging) but also 20 minutes (under-aging) due to the co-segregation among Mg, Si and Li atoms [1]. The results had been predicted by early works [2, 3]. However, the effect of Li addition on microstructure evolution is not well understood. In this work, we conducted 3DAP analyses of a base alloy (Al-0.62Mg-0.93Si, wt.%) and a Li-added alloy (Al-0.55Mg-0.89Si-0.05Li, wt.%) aged at room temperature for 300 and 2100 hours. It was found that the Li-addition increases the number density of clusters which consist of mainly Mg and Si atoms. Further analyses were performed for the Li-added alloys to clarify the positional correlation between Li atoms and the clusters. Although it is difficult to judge the correlation visually as shown in Figure, co-segregation among Mg, Si and Li atoms was confirmed by applying statistical techniques.The detail of the analysis process will show in the presentation to discuss its superiority and limitation. [1] Y. Koshino, M. Kozuka, S. Hirosawa and Y. Aruga, J. Alloy Compd. 622 (2015) 765-770. [2] T. Sato, S. Hirosawa, K. Hirose and T. Maeguchi, Metall. Mater. Trans. A 34 (2003) 2745-2755. [3] S. Hirosawa, T. Omura, Y. Suzuki and T. Sato, Mater. Sci. Forum 215 (2006) 519-521. Figure: (a) Li, (b) Mg and (c) Si map of Al-Mg-Si-Li alloy aged at room temperature for 2100 hours. B22-P-07 doi:10.1093/jmicro/dfv263