不同轧制温度下7075铝合金组织演变规律及对力学性能的影响

Microstructure Evolution of 7075 Aluminum Alloy at Different Rolling Temperatures and Effect on Mechanical Properties

摘要:

随着轧制温度的升高，7075铝合金的组织和力学性能均会发生变化，对商用铸造铝合金在250 ℃、300 ℃、350 ℃ 和400 ℃不同的温度下进行轧制，对比晶粒尺寸和力学性能。实验结果表明，在250 ℃～350 ℃范围内，晶粒尺寸随着轧制温度的升高而增大。采用400℃轧制可获得细化的再结晶组织。同时，随着轧制温度从250℃升高到400℃，试验组7075铝合金的抗拉强度呈现先减小后增大的趋势，在350 ℃存在最低值521MPa，在400 ℃存在最大值570 MPa。而且在400℃的轧制温度下，可获得细晶组织，同时增强了7075铝合金的强度和塑性。拉伸断口的SEM图像也表明，在400 ℃的轧制温度下，材料的断裂方式从偏脆性断裂转变至偏韧性断裂。

Abstract:

Microstructures and mechanical properties of 7075 aluminum alloy changed with rolling temperatures. Commercial as-cast 7075 Al alloy was rolled at 250 oC, 300 oC, 350 oC and 400 oC in this study, respectively. The results showed that the rolling temperature significantly influenced the microstructures and mechanical properties of 7075 Al alloy. The grain size increased as the rolling temperature was raised from 250 oC to 350 oC. However, evident finer recrystallization structure was found by the optical microscope (OM) as the rolling temperature increased to 400 oC, which was the result of dynamic recrystallization during deformation. Meanwhile, the strength of 7075 Al alloy first decreased to 521 MPa when the rolling temperature was 350 oC and then increased to 570 MPa as the rolling temperature was raised to 400 oC. Rolling at 400 oC could refine grain structures and simultaneously improve the strength and ductility. The tensile fracture surface revealed a translation of brittle fracture to ductile fracture with the rolling temperature increasing to 400 oC.