2025 年 64 巻 1 号 p. 7-12
A medium entropy CuAlZnMg alloy was subjected to high–temperature compressive deformation up to 60% nominal strain and the related changes in microstructure and mechanical properties were investigated. The CuAlZnMg alloy, which is hardly plastically deformed at room temperature, was deformed up to 60% strain at temperatures between 673 and 773 K. At the four experimental temperatures, the alloy exhibited a work–softening type stress–strain curve with maximum stress immediately after elastic deformation followed by sharp softening. The microstructure of the as–cast specimen consisted of six phases, comprising brighter elongated bands and other darker areas. High–temperature compressive deformation resulted in a granular or elongated dark phases covered by bright phases at 18% compressive strain and a granular duplex microstructure of a few μm to several tens of μm at 60% compressive strain. Compared to the as–cast mean hardness, the mean hardness of the specimens after high–temperature deformation tended to increase in the order of 18%, 40% and 60% compressive strain. On the other hand, the fracture toughness values did not show a clear increase or decrease with high–temperature deformation. A marked stress drop was observed in the range of 0.4–0.5 absolute true strain during high–temperature compressive deformation. This was attributed to dynamic recrystallisation and the appearance of a liquid phase.
