固溶时效工艺对7055铝合金组织和力学性能的影响

Effects of Solution and Aging Treatments on the Microstructures and Mechanical Properties of 7055 Al Alloys

采用透射电子显微镜、光学显微镜、拉伸力学性能测试等手段比较分析了不同固溶时效工艺对7055铝合金挤压棒材微观组织结构和力学性能的影响规律和机理。结果表明,固溶和时效工艺的合理搭配对控制合金微细结构、获得理想的综合力学性能有重要作用。采用470℃/20 min＋480-490℃/20 min的两级固溶处理可以进一步减少合金中未溶化合物的数量,有利于增加时效强化效果;当第二级固溶温度为490℃时,可以使未溶化合物数量明显减小,其体积分数从单级固溶的2.5%降低至约2.0%;晶粒尺寸在30-35μm。本试验条件下,7055铝合金挤压棒材经470℃/20min＋485℃/20 min两级固溶处理和随后的135℃/16 h＋190℃/10 min两级时效处理,抗拉强度和屈服强度分别达到694和660 MPa,延伸率仍保持14%,合金具有最佳的综合力学性能。

The effects of solution and aging treatments on the microstructures and mechanical properties of 7055 A1 alloy bars were studied by transmission electron microscopy, optical microscopy and tensile mechanical property testing. The results show that an appropriate combination of solution and aging treatments plays an important role in controlling microstructure so as to obtain improved mechanical properties. Two-step solution of 470 ℃/20 min＋480-490 ℃/20 rain could further decrease the amount of undissolved particles and is helpful to enhance age-strengthening. When the 2nd-step solution temperature is increased to 490 ℃, the volume fraction of undissolved particles decreases remarkably, from 2.5% in the case of one-step solution treatment to 2.0%. The grain size of the as-solutioned alloys under experimental conditions is in the range of 30-35 μm. Optimum combined mechanical properties are achieved under the regime of 470 ℃/20 min＋485 ℃/20 min solutiontreatment followed by 135 ℃/16 h ＋ 190 ℃/10 min aging treatment, with the tensile strength and yield strength being 694 MPa and 660 MPa, respectively, in the meantime maintaining a high elongation to failure of 14%.