停放时间对6061铝合金性能及微观组织的影响

采用宏观检测与显微分析相结合的手段,研究不同停放时间下6061铝合金的力学性能与微观组织的变化规律。结果表明:停放时间对6061铝合金的晶粒尺寸有较大影响,晶粒尺寸呈先增大后减小的趋势;停放时间对6061铝合金弹塑性变形过渡阶段有较大影响,但对弹性及塑性阶段变形的影响很小。6061铝合金在停放为0~2 h时,力学性能无明显变化,变形后试样表面光滑,变形协调性较好;停放时间为12 h时,材料的抗拉强度和屈服强度降至最低,但伸长率提高,试样表面呈橘皮形貌,变形均匀性较差;停放时间为24 h^15 d时,合金的强度回升并逐渐趋于稳定。结果表明:随着停放时间的增长,6061铝合金断口的韧窝直径和深度不断增加,第二相粒子的尺寸也不断增大,形状由球状、带状逐渐转变为板状、块状。通过研究得到6061铝合金满足汽车结构强韧化需求,综合性能最优需求的停放时间为12~24 h。此研究结果能够为6061铝合金加工工艺优化提供理论指导。

Influence of quench delay time on mechanical properties and microstructure of 6061 aluminum alloy

The dependence of the mechanical properties and microstructure of 6061 aluminum alloy under different quench delay time were investigated by the combination of macro-detection and micro-analysis. The results show that the quench delay time has a great influence on the grain size of 6061 aluminum alloy, and the grain size increases first and then decreases. The quench delay time has a great influence on the elastic-plastic transition deformation of 6061 aluminum alloy, but has little effect on the elastic deformation. The 6061 aluminum alloy has no obvious change in mechanical properties during quench delay time of 0-2 h. After deformation, the surface of the specimens is smooth and the deformation coordination is better. When the quench delay time is 12 h, the tensile strength and yield strength of the material are minimized, but the elongation increases. Meanwhile, the surfaces of the specimens show the appearance of orange peel and the deformation uniformity is poor. When the quench delay time is 12 h-15 d, the strength of the alloy rises and gradually stabilizes. The results of microscopic analysis show that, with the increase of quench delay time, the diameter and depth of the dimples of the 6061 aluminum alloy fracture increase, and the sizes of the second phase particles also increase. The shapes gradually change from spheres and ribbons to plates and blocks. The optimal quench delay time of 6061 aluminum alloy is 12-24 h. The research results can provide theoretical guidance for the optimization of 6061 aluminum alloy processing technology.