The microstructure, hardness and tensile properties of a new super high strength aluminum alloy with Zr addition

This research is based on the addition of zirconium to a new super high strength Al–12.24Zn–3.25 Mg–2.46Cu alloy. The results showed that Zr addition decreases average grain size (approximately 20%), forms rosette-like microstructure and introduces proper distribution of the second phases. In addition, due to the presence of Al3Zr particles in Zr-refined specimen, the area fraction of recrystallized regions decreased by 65% as compared with unrefined specimen. Furthermore, tensile strength, yield strength and particularly elongation values of the extruded refined sample were enhanced nearly 34%, 25% and 1850%, respectively, when compared with not-extruded unrefined one. Microstructural observations and fractographic examinations of the fractured surfaces of several extruded specimens indicated dimple-like mechanism while the presence of coarse eutectic constituent was responsible for brittle mode of fracture in not-extruded specimens.