Effect Of Rolling Technology On The Microstructure And Properties Of AlMgSi Alloy

In this paper, On the base of AlMgSi alloys, alloy composition are designed,a new type of low-cost automotive aluminum alloy sheet and its rolling technology are developed.Based on the hot rolling under 430℃and then cold rolling experiment, effects of rolling process on microstructures and mechanical properties of alloy sheet are investigated, and recrystallization mechanism in recrystallization annealing after cold rolling are discussed. Meanwhile a comparative study on the microstructures, mechanical properties of alloy at different rolling process but the same heat treatment method are conducted. Finally, the corrosion resistance and its mechanism of the alloy are analyzed.The results show that the electromagnetic stirring AlMgSi aluminum alloy ingot is mainly composed of equiaxed grains.There are a large number of fish-bone-shaped AlFeMnSi phase,strip shaped AlFeSi phase and acicular MgSi phase distribute in the grain and grain boundaries. These phases split the matrix, decrease the strength and plasticity of cast alloy.The tensile strength is 158.6MPa,the extensibility is 5.8% and the hardness is 33.8.After homogenizing annealing, the microstructures change significantly. The segregation disappeared which result in the uniforming of microstructures.As rolled under 430℃at different 1st rolling pass reductions of 13%,33% and 47%, effects of 1st rolling pass reductions and strain intensity on microstructure of hot rolled alloy sheets are studied. Meanwhile,effects of 1st rolling pass reductions on microstructure of anealed cold rolled alloy sheets, and on microstructure and mechanical properties of T6 condition are studied. The results exhibite that, with the increasing of strain intensity, more grains are refined; Compared the results of microstructure and mechanical properties at different rolling process,the results show,with the increasing of 1st rolling pass reductions , microstructure and mechanical properties of alloy sheet are improve obviously.The mechanical properties of alloy are the best,when the 1st rolling pass reductions is 47%. The tensile strength is 398.4MPa,the extensibility is 20% and the hardness is 112. Based on corrosion experiments, the corrosion resistance of cast state,homogenizing annealing state and three different rolled sheet are studied. The saltwater experiments results show the more 1st rolling pass reductions, the better corrosion resistance. Based on intergranular corrosion experiments, the results exhibite that,homogenizing annealing decrease the corrosion resistance of alloy. The exfoliation corrosion resistance of rolled alloy sheet is worse than cast state, but it is much better than homogenizing annealing state.