Abstract
The effects of alloy contents on the strength and toughness of Al–Zn–Mg–Cu alloy T6 extrusion were studied by means of tensile test and Charpy impact test. In this study, the role of the main elements (zinc, magnesium, copper) on the strength and toughness of the Al–Zn–Mg–Cu alloy was systematized on the basis of experimental results. Fundamentally, large amounts of the main elements results in higher strength and lower toughness. Exceptionally, when the sum of magnesium and copper contents exceeds 4.0 mass%, undissolved S–Al2MgCu and/or η-MgZn2 dispersoids exist in the matrix and they cause lower toughness. The higher addition of magnesium and zinc, which compose strengthening η′ phase, has greater effect on strength. On the other hand, copper atoms, which seem to solute in the η′ phase, accelerate the precipitation of η′ phase and have smaller effect on strength compared with magnesium.
