**5.2 Cast-forging**

The mechanical properties of the gravity-cast Al-Mg alloys were increased by hot-forging. The tensile strength and the 0.2% proof stress increased as the Mg content increased. The elongation of Al-8%Mg was greater than that of the other Al-Mg alloys considered in this study. The addition of Fe did not degrade the tensile stress or the 0.2% proof stress. The elongation of all alloys except for the Al-8%Mg was degraded by the addition of the Fe. The elongation of the Al-8%Mg with 0.2%Fe was greater than that of the Al-8%Mg, and that of the Al-8%Mg with 0.4%Fe was the same as that of the Al-8%Mg. The elongation of the Al-8%Mg with 0.8%Fe was 15.6%, which is sufficiently large for a forged aluminum alloy. Al-8%Mg is thus suitable for cast-forging.

## **5.3 Roll casting**

As the Mg content was increased, the tensile stress gradually increased, whereas the 0.2% proof stress remained almost constant. The elongation of the Al-8%Mg was greater than those of the other Al-Mg alloys. The LDR decreased as the Mg content increased. Therefore, the Al-4.5%Mg was selected as the most suitable for sheet forming among the roll-cast Al-Mg alloys. The tensile stress of the Al-4.5%Mg was almost uniform for the added Fe content. The 0.2% proof stress gradually increased with increasing Mg content, and the elongation very gradually decreased. The elongations of the Al-4.5%Mg and Al-4.5%Mg with 0.8%Fe were 30.3% and 28.6%, respectively. The LDR was 2.0 until an Fe content of 0.4%, and then it decreased with increasing Fe content for Fe contents greater than 0.6%. This shows that twice-recycled Al-4.5%Mg (Al-4.5%Mg with 0.4%Fe) cast using the roll-caster can be used for sheet forming.
