光輝性を有する輸送機器ホイール向けAl-Mg-Zn系合金の開発

概要

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The purpose of this study is to develop an Al-Mg-Zn series aluminum alloy for automotive wheels and to determine its appropriate heat treatment condition. Zn was added to AC7A aluminum alloy to improve its mechanical properties, which were characterized by a tensile test. In this study, Zn was added in the range of 2.54.0 mass%. The test results showed that the tensile strength and 0.2% proof stress increased with an increase in the weight fraction of Zn. In addition, the tensile strength was effectively improved by an increase in aging time and heat treatment temperature. However, when the alloy specimen was treated with high temperature under a long aging time, the fracture strain of the aluminum alloy was decreased. Microstructure observation of the specimen suggested that the T-phase (Al2Mg3Zn3) precipitated when Zn was added to AC7A. Furthermore, microscopic observation showed that under a long aging time, the T-phase of the specimen coarsened. Finally, this study demonstrated that the alloy added to 4.0 mass% Zn in AC7A and aged at 453 K for 4 h is applicable as automotive wheels.