長周期積層構造型耐熱 Mg-Zn-Y-Ag 鋳造合金の組織形態と機械的性質

Abstract

The extruded Mg-Zn-Y alloy with long-period stacking ordered (LPSO) structures is known to display increased strength at room temperature as well as at elevated temperature. In order to achieve these attractive properties in cast component, we focused on controlling microstructure of Mg96Zn2Y2 (at%) cast alloy by the addition of Ag. Mg96Zn2Y2 cast alloy is composed of α-Mg phase, LPSO phase and Mg3Zn3Y2 phase, on the other hand, Mg-Zn-Y-Ag cast alloy also had 4th phase by an addition of Ag. By the addition of over 1 at% Ag, the yield strength was significantly increased at room temperature without grain refining. Because Mg-Zn-Y-Ag cast alloy was mainly strengthened with the intermetallic compound, rather than solid solution hardening over 1 at% Ag. Furthermore the yield strength of Mg93Zn2Y2Ag3 cast alloy was 20% higher than that of Mg96Zn2Y2 cast alloy at 473 K.