Development of heat-treatable Al-5Mg alloy sheets with the addition of Zn

For a non-heat-treatable Al-5Mg alloy sheet, Zn was selected as an additive for precipitate hardening in the alloys. As the Zn content increases to 5 wt%, for recrystallized sheets, a high elongation to failure, along with the high tensile strength, was observed due to the activities of deformation band formation and grain boundary sliding. After aging treatment at 120 °C, Al-5Mg-5Zn alloy was reinforced by τ-phase (Mg₃₂(Al,Zn)₄₉) precipitates because the phase is formed the addition of 3.54 wt% Zn in Al-5Mg alloy. The precipitates are effective in the alloy, showing a yield strength of 433.4 MPa, the value of which is 4-times higher than that of Al-5Mg alloy. Thus, for a proper selection when adding Zn element to Al-5Mg alloy, a reinforcement of the strengthening mechanism can be induced, leading to much higher strength without a degradation of the elongation to failure.