关键词: 铝合金棒材, 固溶处理, 组织, 力学性能

Abstract: Effects of solution treatment temperature (450, 470, 490 ℃) and holding time (0.5, 1, 2, 4 h) on microstructure evolution and mechanical properties of extruded rods of 7075 aluminum alloy were systematically studied by means of optical microscope, scanning electron microscope (SEM) combined with energy dispersive spectroscopy (EDS) and universal tensile testing machine. The results show that after solution treatment, with the increase of temperature and the prolongation of holding time, the strip structure along the extrusion direction weakens, and part of second phases dissolve into the matrix. The θ(CuAl₂) phase basically disappears, and only a small amount of T(AlZnMgCu)+η(MgZn₂) phase can be seen in the visual field, which is entangled with the brittle Fe-Si phase. However, when the solution treatment temperature reaches 490 ℃ or the holding time exceeds 2 h, the grains coarsen and the size of the undissolved phase increases. With the increase of solution treatment temperature and the prolongation of holding time, the elongation and tensile strength of the extruded rods of 7075 aluminum alloy both show a trend of first increasing and then decreasing. The optimal solution treatment process is to hold at 470 ℃ for 2 h, under which the alloy has the best strength and plasticity.

Key words: aluminum alloy extruded rod, solution treatment, microstructure, mechanical properties