Effect of prerolling before artificial aging on the mechanical properties of high-Zn-content Al–Zn–Mg–Cu–Sc–Zr–Mn alloy

Abstract

The effect of prerolling before artificial aging on the mechanical properties of the Al–Zn–Mg–Cu–Sc–Zr–Mn alloy with 12.4 wt% Zn (Zn/Mg ratio >1.3 at.%) is studied. The alloy sheets are prepared via casting, homogenization, hot rolling, and solution treatment. The sheets are further cold rolled to reduce their thicknesses by 0%–50% before being artificially aged. Yield strength, ultimate tensile strength, and elongation are increased from 648 to 697 MPa, from 662 to 712 MPa, and from 2.2% to 4.4% by prerolling up to 30%, and prerolling again by 50% reduces both the strength and elongation. Changes in the microstructural features, such as grain morphology, dislocation density, and defect characteristics, are attributed to the variations in the strength and elongation of the alloy. Work hardening during prerolling is responsible for the increase in strength, while pore closure and shear band formation induced by prerolling either increase or decrease the elongation. Furthermore, precipitation kinetics are accelerated by applying prerolling, which facilitates a faster aging response, lesser processing time to reach the peak hardness, and better mechanical properties.

Keywords

• Al–Zn–Mg–Cu–Sc–Zr–Mn alloys
• Prerolling
• Strength
• Elongation
• Pore density