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

The effect of Yb addition on the strength and fracture toughness of Al-Zn-Mg-Cu-Zr aluminum alloy was investigated by measuring tensile properties and fracture toughness. The surface morphology was observed by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that Yb addition can produce fine coherent Yb contained dispersoids. Those dispersoids trend to inhibit Al matrix recrystallization and retain the recovery deformed microstructure. Compared with Al-Zn-Mg-Cu-Zr alloy, Yb contained alloy demonstrates mechanical property improvements from 710 MPa to 747 MPa for ultimate strength, from 684 MPa to 725 MPa for yield strength, from 21 MPa·m1/2 to 29 MPa·m1/2 for fracture toughness with T6 treatment.