Effects of Ca and RE Additions on the Precipitation and Microstructure of As-Cast AZ91 Alloy

Abstract:

The effect of Ca and RE metal additions on the precipitation and microstructure of as-cast AZ91 alloy was systematically investigated. It was found that Ca and RE additions could result in phase and microstructure changes. The XRD pattern showed the crystallite phase of as-cast AZ91 alloys consists of α-Mg matrix and β-Mg₁₇Al₁₂, however, after adding 1.5wt. % Ca and 0.8wt. % RE (0.5wt. % Sm and 0.3wt. % La), peaks coincident with Al₂Ca, Al₂Sm and Al₁₁La₃ intermetallic compounds were found, suggesting the generation of relative precipitates. The SEM images indicated that in as-cast alloys, the Al₂Ca intermetallic compound was located at grain boundaries with a lamellar structure, and the Al₂Sm intermetallic compound was homogeneously distributed in the α-Mg matrix or near the grain boundaries with a polygonal structure, and the Al₁₁La₃ intermetallic compound was located at grain boundaries with a needlelike structure. These intermetallic compounds could reduce the amount of β-Mg₁₇Al₁₂ and refine the microstructure of as-cast AZ91 alloy.

• Periodical: Applied Mechanics and Materials (Volume 865)
• Pages: 30-35
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.865.30
• Online since: June 2017
• Authors: Li Fu, Qi Chi Le*, Pei Li Gou, Xi Bo Wang, Xuan Liu
• Keywords: As-Cast, AZ91 Alloy, CA, La, Microstructure, Precipitation, Sm

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