| dc.description.abstract | In this study, microstructure observation, thermal analysis, mechanical property test and end-quenching test were used to explore the effect of Zn/Mg ratio(4.6/5.4/6.9) and homogenization heat treatment on the mechanical properties, corrosion resistance, quenching sensitivity, and hot workability of AA7095(Al-xZn-yMg-2.4Cu (wt%)) alloys. The results show that the low Zn/Mg ratio alloy with high Mg content, after being homogenized at low temperature (460°C), the active and low melting point S(Al2CuMg) phase precipitates on the grain boundary, which limits the hot working of the alloy. And the solid solution temperature, and become the starting point of alloy fracture, which will result in low hot-workability of the alloy, low corrosion resistance, and low mechanical properties (strength and ductility). When low Zn/Mg ratio alloy with high Mg content is subjected to two stages of homogenization (460°C+485°C), the S (Al2CuMg) phase formed by the low temperature homogenization will be fully dissolved into the aluminum matrix, the damage of S(Al2CuMg) relative to the alloy properties is eliminated.
The alloy with high Mg content of medium Zn/Mg ratio, required to execute two-stages homogenization to eliminate the S(Al2CuMg) phase. However, due to the increase in Zn content, the precipitation power of the alloy strengthening phase η′(MgZn2) is increased, therefore the strength of the alloy also increased. However, due to the high number of non-integrated strengthening phases, the quenching sensitivity of the alloy is also increased. For alloys with low Mg content and high Zn/Mg ratio, after homogenization treatment at low temperature (460°C), there is no precipitation of S (Al2CuMg) phase, so good thermal processing can be obtained under simplified homogenization procedures, alloy with combination of corrosion resistance, mechanical properties (strength and ductility), and low quench sensitivity. | en_US |