2019 年 60 巻 11 号 p. 2435-2441
Al–Mg alloy is a representative non-heat-treatable aluminum alloy. The main strengthening mechanism of the alloy is solid solution hardening by magnesium. If we can increase Mg solubility much more in the solid solutions by using the excellent cooling capacity of the vertical-type high-speed twin-roll casting, further improvement of strength is expected. In this study, high Mg containing Al–8%Mg, 12%Mg and 23%Mg alloy strips were fabricated by using this method, and increase in Mg solid solubility and mechanical properties were investigated. Cold rolling was performed for Al–8%Mg and Al–12%Mg alloy strips. Although some porosities were observed in the mid-thickness region of the as-cast strips, they were reduced by optimizing the casting conditions. The slightly remaining porosities in the as-cast strip could be eliminated by the subsequent cold rolling. The lattice constant of the α-Al phase was calculated from the diffraction peak position of XRD profile, and by which the Mg solid solubility was estimated. The maximum solid solubility was about 12%. The β-Al3Mg2 phase particles which were observed in the original as-cast Al–12%Mg alloy strip were completely dissolved in to the matrix by the subsequent heat treatment. Compared with the typical commercial Al–Mg alloy, such as 5052 or 5083 alloy, the Al–12%Mg alloy sheets fabricated from the twin-roll cast strip had an excellent strength and ductility balance.
