7xxx series aluminum alloy sheet and preparation process thereof

The invention discloses a 7xxx series aluminum alloy sheet and a preparation process thereof. The 7xxx series aluminum alloy sheet comprises the compositions of 1.7-1.9% of Mg, 5.0-6.5% of Zn, 0.25-0.40% of Cu, lass than or equal to 0.10% of Fe, less than or equal to 0.06% of Si, lass than or equal to 0.01% of Mn, less than or equal to 0.01% of Zr, less than or equal to 0.01% of Cr, 0.01-0.03% ofTi, and the balance Al and inevitable elements. The preparation process comprises the following steps that (1), smelting is performed; (2) degassing and filtration are performed; (3) casting is performed; (4) soaking is performed; (5) saw cutting and milling surface are performed; (6) preheating and hot rolling are performed; (7) edge trimming and transverse knife uncoiling are performed; (8) solid solution quenching is performed; (9) stretching is performed; (10) aging is performed; and (11) saw cutting is performed, and aluminum alloy sheet finished products are obtained. The surface hardness of the aluminum alloy s