Intermediate phase analysis of cast Al7075 after the addition of high-temperature oxides

Al7075 is a popular high-strength wrought alloy with higher potential in aerospace sectors. The present research focused on the intermediate phase formation during the casting of Al7075 alloy with the addition of high-temperature oxide additives. The intermediate phases in Al-Zn-Mg-Cu quaternary alloy formed at the grain boundaries or within the grains, and their formation at a specific location can be altered by mechanical, thermo-mechanical, or chemical treatment. A novel approach, adding high-temperature oxides - a chemical treatment, distributes the alloying elements by changing the segregation patterns and forming new phases. It results in microstructural changes that control mechanical properties. The 2.5 weight % of high-temperature oxides, ZrO2, TiO2, and ZrTiO4, were added into the melt of Al7075 alloy by die-casting. The addition of these oxides formed intermediate phases such as ƞ(MgZn2), S(Al2MgCu), and T(Mg3Zn3Al2) depending on the Zn/Mg ratio. XRD analysis finds the formation of different intermediate phases. The SEM-EDS analysis at different locations confirmed their presence. The elemental ratios of Zn/Mg decide the formation of intermediate phases and, based on their proportion, different phases were confirmed. Among ZrO2, TiO2, and ZrTiO4 addition, the ZrO2 addition alters the mechanical properties of Al7075.