Effect of silicon addition on the composition and structure of fine-scale precipitates in Al-Mg-Si alloys

• Published in: Scripta materialia Vol. 36; no. 1; pp. 89 - 93
• Main Authors: Maruyama, N., Uemori, R., Hashimoto, N., Saga, M., Kikuchi, M.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 1997; Elsevier Science
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid-phase precipitation; Magnesium additions; Precipitation; Aluminium base alloys; DSC; Electron diffraction; Alloying effects; Ternary alloys; Experimental study; Microstructure; Precipitates; TEM; Silicon additions
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/S1359-6462(96)00358-2

Field-emission TEM has been used to study the composition and structure of precipitates formed on aged Al-Mg sub 2 Si and excess Si containing Al-Mg sub 2 Si alloys. The compositions of beta " and beta ' are Si-rich and becomes close to Mg:Si=2 as precipitation proceeds in both alloys. Moreover, Mg:Si ratio of the precipitates becomes small with increasing excess Si content, although the structure of precipitates is not strongly affected by Mg:Si ratio of the alloy. Structure of beta " is determined to be monoclinic a=0.714plus/minus0.017, b=0.658plus/minus0.013, c=0.405[nm], gamma =75plus/minus1 deg , with the orientation relationship between beta "-Al matrix, [100] sub beta //[210] sub Al , [010] sub beta " //[230] sub Al .