Effect of Heating Rate for Solid Solution on Microstructure and Properties of Al-10.78Zn-2.78Mg-2.59Cu Aluminum Alloy

Al-10.78Zn-2.78Mg-2.59Cu aluminum alloy was heated to 470℃ at the heating rates of 3.6℃·h^-1 and 180℃·h^-1, respectively, then treated by solid solution, and aged subsequently. The effects of heating rate on the microstructure and properties of tested alloy were studied. The results show that the average grain size and the average orientation angle of grain boundaries in tested alloy at the relatively high heating rate was higher, the fraction of low angle grain boundaries was smaller, the mechanical properties were lower and the conductivity was higher than those at the relatively low heating rate. Dimples existed obviously on the tensile fracture of tested alloy at the two heating rates, and the fracture modes were both transgranular. The effect of heating rate on corrosion resistance was little; the intergranular corrosion depth was between 30 μm and 100 μm, the intergranular corrosion grade was 3, and the peeling corrosion grade was PC. The solid solution and aging precipitation strengthening made the most important contribution to yield strength of the tested alloy. Heating up slowly can improve yield strength of the tested alloy effectively.