Aluminum base aluminum magnesium alloy substrate for hard disk and manufacturing process of aluminum base aluminum magnesium alloy substrate

The invention discloses an aluminum base aluminum magnesium alloy substrate for a hard disk. The substrate comprises, by mass percentage, 3.5% to 6.0% of Mg, 0.05% to 0.1% of Cr, 0.01% to 0.1% of Cu, 0.05% to 0.4% of Zn, not larger than 0.01% of Si and not larger than 0.01% of Fe. The tensile strength of an aluminum silicon eutectic alloy rod for welding ranges from 210 MPa to 250 MPa and the elongation ranges from 14% to 20%. By the adoption of the aluminum base aluminum magnesium alloy substrate for the hard disk, the content of Si and the content of Fe are limited, so that the largest length of an Al-Fe system intermetallic compound is below 6 micrometers, and the largest length of a Mg-Si system intermetallic compound is below 3 micrometers. The quantity of the intermetallic compounds is quite small, and under the view of a Leica microscope 500 x, the number of corrosion holes of the intermetallic compounds is smaller than or equal to 50.