| 7N01 Al alloy is a high strength, weldable aluminum alloy. It has attracted a broad range of attentions in high-speed train component filed by its excellent characteristics such as low density, ease of processing, well heat deformation resistance performance, wide range of quenching temperature, excellent welding performance and good corrosion resistance. In this paper, the samples with two different aging treatment of T6(120℃/24h) and T6I4(120℃/30min+60℃/20d) were prepared. The 7N01-T6 alloy and 7N01-T6I4 alloy was investigated in dynamic impact testing of 900s-1, 1900s-1, 3300s-1, 4500s-1, 5800s-1 at 20℃, 150℃, 250℃, 350℃ by split Hopkinson’s pressure bar(SHPB) technique and in quasistatic compression of 0.001s-1, 0.01s-1, 0.1s-1 by material testing machine at 20℃. The effect of aging treatment, strain rate and temperature on the property and evolution mechanism of organization of 7N01 aluminum alloy were investigated through microstructural analysis by metallographic and transmission electron microscopy(TEM).1) The precipitated phase in 7N01-T6I4 Al alloy is denser and finer than 7N01-T6 Al alloy, the results of dynamic compression test at room temperature indicated that the dislocation pileup density and the stress for dislocation pileup collapse in 7N01-T6I4 Al alloy are higher than that of 7N01-T6 Al alloy. Compared to 7N01-T6 Al alloy, the shear stress that 7N01-T6I4 Al alloy can bear is lower. The dynamic yield stress and flow stress as well as impact resistance of 7N01-T6I4 alloy are larger than 7N01-T6 alloy.2) Under the impact test at 150 ℃ and the strain rate lower than 4500s-1, precipitated phase appears to dissolve and the density decreased with the increase of strain rate. The dissolve of precipitated phase in 7N01-T6 aluminum alloy is found more obvious than 7N01-T6I4 aluminum alloy. As the strain rate increases to 5800s-1, the energy absorbed by the alloy increases, and the effect of temperature increment due to adiabatic shear strengthenes. After impact, for the 7N01-T6 alloy, the precipitated phase begins to coarsen for the phases that larger than the critical size, but the phases size less than the critical size are dissolved. But only part of the precipitated phases are dissolved in the 7N01-T6I4 alloy. Therefore, it can be conclude that under impact test at 150℃, the dynamic yield stress, flow stress and hardness of the 7N01-T6I4 alloy are higher than that of 7N01-T6 aluminum alloy.3) Under the impact test at 350℃, the precipitated phases of 7N01-T6 alloy begin to coarsen. For 7N01-T6I4 alloy, re-dissolution of precipitated phases and dynamic recrystallization organization have appeared, and the precipitated phases are basically dissolved under 350℃ test. So the dynamic yield stress and flow stress as well as impact resistance of 7N01-T6 alloy are larger than 7N01-T6I4. |
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