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 degrees C, Al-5Mg-5Zn alloy was reinforced by tau-phase (Mg-32(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.