The Effect of Growth Rate on the Microstructure and Mechanical Properties of 7020 Alloys

The 7020 aluminum alloy is one of the hardenable Al-Zn-Mg based alloys, which are a family of high strength aluminum alloys. These 7020 alloys are commonly used in the aircraft and automotive industries. The microstructural changes have a significant impact on the mechanical properties of binary and multi-component alloys. For this reason, 7020 aluminum alloys were prepared with different growth rates on account of the changes in the microstructures; thus, directionally solidification processes were actualized with a Bridgman furnace at five various growth rates (V = 8.3-166.0 mu m/s) and at constant temperature gradient (G = 8.3 K/mm). Microhardness (HV), ultimate tensile strength (sigma(U)) and yield strength (sigma(y)) of the solidified alloys were determined. The HV increased from 758.8 to 917.1 N/mm(2), the sigma(U) from 125.4 to 208.1 N/mm(2) and the sigma(y) from 133.7 to 230.8 N/mm(2) with an increase in growth rate from 8.3 to 166.0 mu m/s.