Effects of quenching cooling method and macro-orientation on mechanical properties of Al-Zn-Mg-Cu alloys

Abstract

The 7050 aluminum alloy was studied as the research object to investigate the coupling effect of heat treatment state （air quenching aging and water quenching aging） and macroscopic orientation （0°， 45°， and 90° concerning the rolling direction） on mechanical properties of the alloy. The results indicate that the precipitated phases in the water-cooled aged samples are small， uniformly dispersed， and the grain boundaries have narrow precipitate free bands. In the air-cooled aging state， the supersaturated solutes not only form coarse precipitates with semi coherent Al3Zr as the core， but also precipitate a large amount along dislocations. In addition， compared with the water-cooled aging state， the grain boundary phase size in the air-cooled aging state increases significantly， and the precipitate free zone at the grain boundary widens significantly. The strength and elongation of samples with different macroscopic orientations are significantly reduced. The influence of macroscopic orientation on the difference in strength between two states of samples is relatively minimal， but it has a significant impact on the difference in elongation. When the tensile direction is at 45° to the rolling direction， the decrease in elongation induced by air cooling is the slightest， while the tensile direction is at 90° to the rolling direction， the maximum decrease is observed.

Keywords

• al-zn-mg-cu alloy
• precipitate
• quenching sensitivity
• texture