Research On Microstructure And Properties Of Al-Mg-Si-Fe Alloy For Rare Earth Modification And Heat Treatment

With the development of industry, people required more for the comprehensive properties of aluminum alloy material. Al-Mg-Si-Fe alloy belonged to Al-Mg-Si series aluminum alloy, was a kind of deformation aluminum alloy, mainly used for hot extrusion production construction and industrial aluminum.so it had certain requirements on the hardness, strength, corrosion resistance properties, etc. Using the purification, refinement and modification effect of rare earth could well to improve the organization and performance of alloy. Besides, homogenizing annealing process had great influence on the comprehensive properties of the alloy. It was an important process before aluminum extrusion processing. So, by rare earth modification and proper homogenizing annealing process on Al-Mg-Si-Fe alloy was of great practical significance.Studied on the microstructure and properties changed of Al-Mg-Si-Fe alloy after adding rare earth Ce:The coarse eutectic compounds of inhomogeneous composition in grain boundary disappeared gradually and the grain size refinement. When the addition content of Ce was 0.35%, most of the organization of ?-Al uniform grain size distribution. The whole feature seemed equiaxial crystal. The average grain size was about 52 ? m. Bulky and bifurcation needle flake iron rich phase in grain interior and boundary translated into Small, independent granule, short iron-rich phase. Rare earth Ce could promote Al9Fe2Si2 phase into Al8Fe2Si phase to a certain degree. The hardness of alloy increased from 35.1 HB to 46.7 HB after adding Ce. It mainly made use of the fine-grain strengthening and dispersion strengthening of Ce, followed by limited solid solution strengthening. Rare earth Ce could improve the corrosion resistance of alloy. When the addition content of Ce was 0.35%, the corrosion resistance of alloy was the best. The quality of the alloy relative loss rate was 57% without Ce at this point.Directly homogenizing annealing treatment for Al-Mg-Si-Fe alloy ingot, observing the ingot casting microstructure and performance changed before and after annealing. The organization of as-cast Al-Mg-Si-Fe alloy was irregular mesh. There was coarse eutectic at the grain boundary. The iron-rich phase in alloy was Al8Fe2Si. Its morphology was short rod and thin strips and had the development trend to needle flake. After homogenizing annealing treatment, some short rod-like Al8Fe2Si phase translated into discontinuous graininess. The best homogenizing annealing process of Al-Mg-Si-Fe alloy was 565? annealing temperature and 7h holding time. By this time, the second phase number and size in alloy relative to the minimum, and the hardness of alloy tend to be stable was 42.8 HB. In conclusion, the best rare earth Ce addition was 0.35% in Al-Mg-Si-Fe alloy. The proper homogenizing annealing process of ingot casting was 565? annealing temperature and 7h holding time.