Effect of extrusion ratio on the microstructure and property of the Al–Zn–Mg–Cu alloy prepared by spray conform

Abstract

The commercial Al-5.72Zn-2.36Mg-1.66Cu (7075) alloys were prepared by the spray Conform (SC) technique consisting of the spray forming and Conform extrusion. The extrusion ratio (ER) was selected as the variable parameter to study the influence mechanism on the microstructures and properties while keeping the other parameters unchanged. The microstructures and properties were investigated by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), x-ray diffraction (XRD), electron backscatter diffraction (EBSD) and tensile tests. Concretely, the changing rules of the grains, second phases, tensile strength and elongation with ER were researched respectively. Results indicate that a fine equiaxed grain microstructure with low level of segregation and porosity was achieved by SC. And the intergranular and intragranular phases were fine and homogeneous before and after retrogression and re-aging (RRA). The dispersion and tensile strength are positive to ER, but the grain size (GS) is inverse. Meanwhile, the elongation increases firstly and then decreases with increasing ER.