*2.1. Material*

The material used in experiment was the 7075 aluminum alloy plate with a thickness of 4 mm and a heat treatment temper of T651. The chemical compositions (in wt.%) were: 5.71% Zn, 2.45% Mg, 1.5% Cu, 0.18% Cr, 0.17% Fe, 0.06% Si, 0.034% Mn, 0.019% Ti, and a balance of Al.
