Effect of micro-alloying on the characteristics of as-cast Al-Zn-Cu-Mg-X alloy with varying Cu and Zn

There is a high demand for lightweight, high-strength materials in the aerospace industry today. Because different microelements play a significant role in the properties of the alloy, a thorough study is essential before conceptualizing any alloy. The current work examines the microstructural, mechanical, and thermal properties of various microalloying elements such as Zr, Ti, Sr, and Sc with varying Cu and Zn percentages. Without adding micro alloys, increasing Cu with less Zn causes a change in grain morphology from irregular equiaxed cellular to uniform dendritic structure with increasing residual eutectic phase content and promotes grain refinement mechanism of as-cast alloys. The addition of Zr+Ti+Sr generally improves Al3M type precipitation as well as eutectic phases, promoting further grain refinement and exhibiting higher hardness and strength than the base alloys. Further enhancement of precipitation has been observed by adding a small amount of Sc with Zr+Ti+Sr exhibiting maximum hardness and tensile strength regardless of the Cu and Zn percentages. Furthermore, the addition of Zr+Ti+Sr as well as Sc improve the elongation of these cast alloys compared to the base alloys without microalloying elements. Most notably, alloys with Sc demonstrates the highest elongation as well as strength regardless of Cu and Zn percentages. The thermal properties of the alloys demonstrate a higher transition temperature (Tg) with increasing Cu percentage without microalloying elements. The addition of micro alloying elements increase the Tg, and the highest Tg of 507 degrees C has been observed with Sc and Zr+Ti+Sr addition.