Abstract: Microstructure and properties evolution of 6016 aluminum alloy intermediate annealed at different temperatures were analyzed using metallographic microscopy, scanning electron microscopy, X-ray diffraction and mechanical performance testing machines. The results show that under different annealing temperatures, the mechanical properties of the 6016 aluminum alloy do not change much, but hemming factor f and Δr value change significantly. The values of f (0.60) and Δr(0.24) at the intermediate annealing temperature of 360 ℃ are lower than the values of f (0.75) and Δr(0.28) at the intermediate annealing temperature of 410 ℃, indicating that the hemming property at the intermediate annealing temperature of 360 ℃ is better than that at the intermediate annealing temperature of 410 ℃. As the annealing temperature increases, the surface grain size and grain boundary precipitate Mg₂Si phase size also increase, the maximum size of Mg₂Si phase increases from 1.41 μm to 2.09 μm, and the morphology of most Mg₂Si phase change from rounded to elongated. The proportion of Cube texture and R texture at the intermediate annealing temperature of 360 ℃ is 12.04% and 5.37%, respectively. The proportion of Cube texture and R texture at the intermediate annealing temperature of 410 ℃ is 14.25% and 3.43%, respectively. Among them, the proportion of R texture at the intermediate annealing temperature of 360 ℃ is higher, which reduces the Δr value and is conducive to improving the hemming property. The crack propagation of the 6016 aluminum alloy at the intermediate annealing temperature of 410 ℃ is faster than that at the intermediate annealing temperature of 360 ℃, which is related to the coarse Mg₂Si phase on the grain boundaries.

Key words: 6016 aluminum alloy, intermediate annealing temperature, grain boundary precipitate, texture, mechanical properties, hemming property