Effect of Total Zn + Mg Content on Precipitation and Strength–Ductility Balance in Al–Zn–Mg Alloys with Zn/Mg = 1

Al-Zn-Mg alloys are age-hardenable aluminum alloys that achieve high strength through precipitation strengthening, making them widely used for structural components requiring a high specific strength.The Al-Zn-Mg alloys exhibit the greatest strengthening potential, primarily due to the formation of η and T phases.Micro-Vickers hardness measurements revealed that increasing the total (Zn + Mg) content enhances both the as-quenched and peak-aged hardness, while reducing the time to reach peak hardness.Tensile testing showed that higher (Zn + Mg) content increases ultimate tensile strength and proof stress but decreases ductility.The ηA/η phases play a dominant role in strengthening compared with the TA/T phases.The mechanical properties of Al-Zn-Mg alloys are strongly influenced by microstructural features such as precipitate distribution, precipitate-free zone (PFZ) width, and grain size.Alloys with a higher precipitate number density and narrower PFZs generally exhibit higher strength but lower elongation.Achieving a microstructural condition that provides high hardness and tensile strength without sacrificing elongation is therefore essential for enhancing the overall mechanical performance of Al-Zn-Mg alloys.