The invention discloses a thermomechanical treatment preparation method of a high-
toughness Al-Mg-Si
alloy plate and application of the high-
toughness Al-Mg-Si
alloy plate in a
new energy automobile covering part. The
alloy comprises, by
mass, 1.0%-1.5% of Si, 0.8%-1.2% of Mg, 0.4%-0.8% of Cu, 0.55%-0.95% of Mn, 0.08%-0.20% of Cr, 0.05%-0.30% of Zn and the balance Al and impurities, the ratio of Mg to Si is 1.2%-2.0%, and the ratio of Mn to Cr is 3.0%-4.5%. The preparation method comprises the following steps:
smelting,
cutting the head and the
tail, milling the surface, carrying out graded homogenization (290-310 DEG C * 6-10 h + 550-570 DEG C * 10-14 h), carrying out hot rolling to 5-6 mm, carrying out
solid solution
quenching (540-570 DEG C * 0.5-1.5 h), carrying out pre-aging (70-90 DEG C * 10-14 h), carrying out cold rolling to 1-2 mm, and carrying out
artificial aging (170-190 DEG C * 0.5-2 h). The method is used for
new energy automobile covering parts,
battery pack cover plates or automobile door anti-collision beams, and the endurance mileage is remarkably increased.