Fracture toughness of Al−Zn−Mg−Cu alloys

1. Reducing the concentration of alloying elements in Al−Zn−Mg−Cu alloys to the lower limit of GOST specifications, and also the concentration of impurities, leads to an increase of the toughness KIC, Magnesium has the largest effect on the toughness. 2. The toughness of Al−Zn−Mg−Cu alloys depends on the structural condition of the alloy. For semifinished products with a recrystallized or partially recrystallized structure the value of KIC is higher than for products with an unrecrystallized structure. 3. The critical size of the defect leading to failure under a stress of 0.5 σ0.2 varies from approximately 0.3 to 1.2 cm, depending on the chemical composition of an alloy of the V95 type.