Effect of Ca addition on selective oxidation of Al₃Mg₂ phase in Al-5 mass% Mg alloy

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>This study examined the effect of Ca addition on the selective oxidation of the Al<SUB>3</SUB>Mg<SUB>2</SUB> phase in an Al-5 mass%Mg alloy during oxidation at 400 °C and 500 °C for 72 h. Ca addition led to the formation of the Al<SUB>4</SUB>Ca and Laves_C36 phases besides the primary Al solid solution and Al<SUB>3</SUB>Mg<SUB>2</SUB>. After the oxidation test, there was no significant oxidation in both the Ca-free and Ca-added alloy samples and no visible change in the surfaces between them at 400 °C, which is lower than the melting temperature of Al<SUB>3</SUB>Mg<SUB>2</SUB> (451 °C). At 500 °C, the surface of the Ca-free alloy showed the formation of oxide blisters, which was not observed in the Ca-added alloy. The presence of an Al<SUB>4</SUB>Ca phase at the grain boundaries led to the formation of multi-element oxides containing Al, Mg, and Ca, which can contribute to the formation of a compact oxide layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ca addition in Al-Mg alloy forms two Ca based intermetallic compounds. </LI> <LI> Coexistence of Al<SUB>4</SUB>Ca and Al<SUB>3</SUB>Mg<SUB>2</SUB> phases forms Ca-Mg-Al based oxides after oxidation. </LI> <LI> Ca-Mg-Al based oxides control oxide blister formation from Al<SUB>3</SUB>Mg<SUB>2</SUB> during oxidation. </LI> </UL> </P>