Zhuo Zhang

Effect of Yb additions on microstructures and properties of 7A60 aluminum alloy

Abstract Al-Zn-Mg-Cu-Zr alloys containing Yb were prepared by cast metallurgy. Effect of 0.30% Yb additions on the microstructure and properties of 7A60 aluminum alloys with T6 and T77 aging treatments was investigated by TEM, optical microscopy, hardness and electric conductivity measurement, tensile test and stress corrosion cracking test. The results show that the Yb additions to high strength Al-Zn-Mg-Cu-Zr aluminum alloys can produce fine coherent dispersoids. Those dispersoids can strongly pin dislocation and subgrain boundaries, which can significantly retard the recrystallization by inhibiting the nucleation of recrystallization and the growth of subgrains and keeping low-angle subgrain boundaries. Yb additions can obviously enhance the resistance to stress corrosion cracking and the fracture toughness property, and mildly increase the strength and ductility with T6 and T77 treatments.

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•m(superscript 1/2) to 29 MPa•m(superscript 1/2) for fracture toughness with T6 treatment.

Effect of Yb Additions on Microstructures and Properties of High Strength Al-Zn-Mg-Cu-Zr Alloys

The effect of 0.30 Yb (mass fraction,%) additions on the microstructure and properties of high strength Al-Zn-Mg-Cu-Zr aluminum alloys has been investigated by TEM, optical microscopy, hardness and electric conductivity measurement, tensile test, stress corrosion cracking test. The results show that the ytterbium additions to high strength Al-Zn-Mg-Cu-Zr aluminum alloys significantly inhibited recrystallization during solution treatment. The tensile and yield strengths, elongation, hardness, electric conductivity and stress corrosion cracking resistance of the Yb-containing alloys are improved compared to the alloys without Yb additions. By Yb additions, the critical stress intensity (KISCC) is enhanced from 7 MPa·m1/2 up to 14.5 MPa·m1/2 with the improvement of the strength and ductility. The mechanism for the property improvement from Yb additions has been discussed.