| 6000 series aluminum alloy is one of the ideal materials for automotive light weight because of their excellent properties. However AA6016 has a weak application in Chinese automobile industry, so it is nessary to build a database of the microstructure and the mechanical properties of AA6016, which is of great significance for car companies to choose raw materials and to improve their processing technologies. The main forming process of aluminum panel includes drawing, flanging and hemming, and the bendability which is relevant with flanging and hemming is a key property in the application of aluminum alloys on cars. In this work, three aluminum alloys-A6K21, B6016 amd C6016 supplied by Changan Motor Company are investigated. The microsturctures are obtained by OM, SEM and XRD techniques and the mechanical properties are obtained by uniaxial tension tests. After having a proper fresh solution heat treatment, the effect of natural aging on the bendability of these three materials is investigated through tension and bending tests and SEM techniques. Conclusions can be drawed as followings:① Differences of microstructures and mechanical properties are exsited between the three materials: A6K21 has the highest amount of Mg and B6016 contains the highest amount of Si, Mn and Fe, whereas C6016’s Cu is the most. The grains of the three materials are nearly equiax crystalline grains, the sizes of RD direction and TD direction are nearly the same, but the sizes of ND direction are shorter, and the average sizes of ND side of the three materials are about 32.5μm(A6K21), 23μm(B6016) and 46.5μm(C6016). All the three materials have evident constitutes and dispersoids, the content of constitutes and dispersoids of B6016 is higher than the other two, and the sizes of constitutes and dispersoids of C6016 are higher than that of A6K21 and B6016. The three materials don’t have obvious deformation textures(S, Copper, Goss, Brass) but obvious recrystallization textures(Cube, R, Brass-R). Among the three materials, C6016 has the highest yield strength and tensile strength, while the ratio of yield strength and tensile strength of A6K21 is higher than that of the other two. For the three materials, the strength of RD direction is the highest and the strength of TD direction is the lowest and the elongation of 45°direction is the highest. The n value of B6016 is the highest and the n value of C6016 is the lowest. The r value of A6K21 is the highest and that of C6016 is the lowest, for the three materials, the r value of 45°direction is much lower than the other two directions. The simulations and the practical processing results in the factory show that some parts of the panel are easy to produce cracks because of their huge deformation rates. C6016 has severe cracks in some parts after being drawed and A6K21 exsits some small cracks after being flanged, while B6016 would complete the whole forming process without producing any cracks.② The effect of natural aging on the bendability of the three materials: In this work, some fresh solution heat treatments of schdules of 540℃,550℃,560℃ with 10 minutes are added to the three materials. After a verification, it finds that these fresh solution heat treatments will not affect the grains and textures of the three materials, but they will dissolve some second phases to the matrix. So, this work imply a fresh solution heat treatment of 550℃ with 10 minutes to these samples before bending. Results show that as the natural aging time increases, the strengths and bendabilities of the three materials decreases. At the same aging time, the bendability of A6K21 is best and the bendability of C6016 is worst. The bendability of samples of 0°direction is much worse than the other two directions(90°and 45°). The analysis of the microstructures shows that precipitation effect, the grain sizes, the distributions and sizes of constitutes, the recrystallization textures and the anisotropy of strengths may be the reasons of the bending results. |
PDF Full Text Request