Achieving 800 MPa-level ultra-high strength and satisfactory ductility in Al-Zn-Mg-Cu alloy via trace Y modification

Authors:
  • SYShuo Yuan
    Shuo Yuan
  • YHYang Huang
    Yang Huang
  • ZLZeyu Li
    Zeyu Li
  • XYXuanwei Ye
    Xuanwei Ye
  • MPMulan Peng
    Mulan Peng
  • YTYa Tang
    Ya Tang
  • LHLanping Huang
    Lanping Huang
Preprint
Publisher website
Google Scholar
Abstract
Achieving a superior combination of ultra-high strength and satisfactory ductility remains an arduous challenge in aluminum alloy design. In this work, an Al-Zn-Mg-Cu alloy containing 0.1 wt.% Y is prepared by conventional casting and exhibits an ultimate tensile strength of 804 MPa together with a superior elongation of 8.0%. The results reveal that 0.1 wt.% Y addition refines the average as-cast grain size from 92 to 53 μm. Density-Functional-Theory calculations demonstrate the mutual substitution of Y and Zr on the minority sublattice is thermodynamically favorable, which promotes the transformation of Al3Zr to Al3(Zr,Y) dispersoids during homogenization process. The high diffusion coefficient of Y atom promotes the uniform and high-density precipitation of Al3(Zr,Y) dispersoids. These Al3(Zr,Y) dispersoids, characterized by a higher number density and smaller size, exert a stronger Zener pinning effect and reduce the recrystallization fraction of alloy from 18.9% to 7.6%. TEM and APT results show the trace addition of Y does not alter the precipitation kinetics or size distribution of η′ phase during aging process. But excessive Y will generate coarse insoluble secondary phases, which induce stress concentration and initiates cracking during deformation and thus reduce the alloy’s ductility.

This publication has 49 references indexed in Scilit: