弯曲半径和时效制度对7475铝合金蠕变时效成形的影响

Effects of Bending Radius and Ageing Conditions on the Creep Age Forming of 7475 Aluminum Alloy

基于单曲率弯曲蠕变成形装置,针对7475铝合金板材进行了一系列蠕变时效成形实验,测得了不同时效制度和弯曲半径下的回弹量。采用电导率、维氏硬度、金相显微镜、透射电子显微镜和室温拉伸等手段分析了蠕变时效试样的性能与微观组织,并与人工时效试样进行了对比分析。结果表明:回弹量随着弯曲半径的减小、时效时间的延长和时效温度的升高而降低;弯曲蠕变时效试样比人工时效试样具有较高的屈服强度和抗拉强度,延伸率则相反;随着弯曲半径的增大,屈服强度和抗拉强度均呈现出先增后减的规律,在弯曲半径为1200 mm附近存在峰值;弯曲蠕变时效后试样的晶粒尺寸和形状与人工时效试样无明显区别,其析出相则比人工时效试样更为细小和致密。

Based on the single curvature bending creep forming device, a series of creep age forming tests of 7475 aluminum alloy sheets were conducted. The springback of formed samples with different ageing conditions or bending radiuses were measured. Then the properties and microstructures of the creep ageing formed samples were studied by electric conductivity tests, Vickers hardness tests, optical microscopy tests, transmission electron microscopy tests and tensile tests, respectively. And the results were compared with the artificial aged samples. The results show that the springback decreases with the decreasing bending radius, the increasing temperature and ageing time. The yield strength and the tensile strength of the bending creep ageing formed samples are higher than the artificial aged samples, but the elongation is the opposite. As the increasing of the bending radius, both the yield strength and the tensile strength increase first and then decrease, and the peak value appears near the bending radius of 1200 mm. No clear difference exists in the size and shape of grains between the creep aged samples and the artificial aged samples, the size and the particle spacing of the precipitates of creep aged samples are smaller than the artificial aged samples.