Abstract: A weldable aluminum alloy workable into sheet form containing Si, Mg and Cu, and a process for its production are disclosed.The alloy comprises (in percent by weight) proportions of Si and Mg as defined by a trapezium having the following co-ordinates:______________________________________ Si Mg ______________________________________ (A) 0.5 0.1 (B) 0.5 0.2 (C) 1.3 0.5 (D) 1.3 0.1 ______________________________________Cu: 0.1-0.5;Mn: 0-0.2;Ti: 0-0.1;Fe: 0-0.35;other impurites each: .ltoreq.0.05total impurity content: .ltoreq.0.15balance Al.The production procedure comprises semi-continuous or continuous casting of blanks, an optional homogenisation operation, a hot transformation operation which is terminated in the range of 270.degree. to 340.degree. C., an optional cold transformation operation, a complete solution treatment, a shaping operation using stamping or pressing, folding, bending, etc . . . , and a tempering operation.