Effect of addition of Yb on strength and toughness of Al-Zn-Mg-Cu-Zr high-strength aluminum alloy

Effect of addition of Yb on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Zr high-strength aluminum alloy was investigated by measuring tensile properties and fracture toughness, optical and SEM/TEM microscopy. The mechanisms of strengthening and toughening by addition of Yb were analyzed. The results show that when Yb is added to 7A60 alloy, Yb-containing dispersoids can be produced retaining the deformation-recovery Al matrix without obvious sub-grain boundary in the alloy and inhibiting Al matrix recrystallization. By the addition of 0.3% Yb to 7A60 alloy, the intergranular fracture and the second intergranular cracks decrease markedly, and σb increases from 710 MPa to 747 MPa, σ0.2 increases from 684 MPa to 726 MPa, and KIC increases from 21.6 MN/m3/2 to 29.3 MN/m3/2, respectively.