Study of Ageing Treatment on Spray Forming Al-Zn-Mg-Cu Alloy

The Al-Zn-Mg-Cu (7A04) alloys were prepared by using the method of spraying forming and the hot extrusion. The changes of microstructure and mechanical properties of the spray deposited Al-Zn-Mg-Cu alloy underwent ageing, regression and reageing treatment (RRA) was studied by scanning electron microscopy, X-ray diffraction and other methods. The results show that the tensile strength of the alloy aged at 120 degrees C for 24 hours can reach the peak value (760MPa), but the elongation is only 4.8 percent. The toughness of the alloy regression treated at 160 degrees C for 2 hours can increase to 9.0 percent, but its tensile strength decreases greatly (680MPa). The reaging treatment at 120 degrees C can make the tensile strength up to 740MPa, while the elongation which is 8.2 percent still keeps a higher level.