6016铝合金低温形变热处理行为的研究

发布时间：2019-05-11 00:36

【摘要】：铝合金是轻量化首选的金属材料,发展高强韧性铝合金是扩大其在结构材料上应用的关键,形变热处理工艺对铝合金的力学性能有很大影响。本工作对固溶态、预时效态和T6态6016铝合金的低温形变热处理行为进行了深入研究,三种状态的铝合金经过低温下轧制以及后续低温时效后,力学性能和组织的变化各不相同。固溶态铝合金低温轧制后屈服强度是轧制前的6.5倍,但是伸长率严重下降,再经过低温时效后,伸长率得到显著改善。观察微观结构特征发现,低温轧制能抑制动态回复,形成高密度的位错和变形亚结构,并细化晶粒组织,对合金有很大的强化作用。低温时效时,同时发生强化相析出和回复或部分再结晶作用,使时效后的铝合金在拉伸时有更高的的加工硬化率,这是改善延展性的关键。预时效态铝合金低温轧制后获得更高的强度,但是伸长率也更低,再经过低温时效后,可使强度和伸长率都进一步提高。轧制后强度的提高是由于时效强化、位错和晶界强化共同作用的结果。预时效能加快低温时效时强化相的析出速度,对力学性能的提高有重要作用。T6态铝合金低温轧制后拥有最高的强度,但是伸长率最低,高的强度主要来自时效强化作用。再经过低温时效后强度减小,伸长率也没有明显改善,分析微观组织演变特征发现,低温时效时形成强化效果更低的析出相,铝合金的加工硬化能力也下降。论文还讨论了不同的强化机理对三种状态的铝合金在低温形变热处理过程中强度的贡献。结果得出,随着低温轧制前铝合金时效程度的增加,低温形变热处理过程中时效强化作用逐渐提高,位错和晶界强化作用逐渐下降。
[Abstract]:Aluminum alloy is the preferred metal material. The development of high strength and toughness aluminum alloy is the key to expand its application in structural materials. The deformation heat treatment process has a great influence on the mechanical properties of aluminum alloy. In this work, the mechanical properties and microstructure of 6016 aluminum alloys in solid solution state, pre-aging state and T6 state were studied. The mechanical properties and microstructure of the three states aluminum alloys were different after rolling at low temperature and subsequent low-temperature aging. The mechanical properties and microstructure of aluminum alloys in three states were different after low-temperature rolling and subsequent low-temperature aging. The yield strength of solid solution aluminum alloy after low temperature rolling is 6.5 times higher than that before rolling, but the extension rate decreases seriously, and then after low temperature aging, the yield strength is significantly improved. It is found that low temperature rolling can inhibit dynamic recovery, form high density dislocation and deformation substructure, and refine grain structure, which has great strengthening effect on the alloy. At low temperature aging, the precipitation and recovery of strengthening phase or partial crystallization occur at the same time, which makes the aged aluminum alloy have a higher processing hardening rate during drawing, which is the key to improve the extensibility. After low temperature rolling, the strength of preaging aluminum alloy is higher, but the elongation is also lower. After low temperature aging, the strength and extension of aluminum alloy can be further improved. The increase of strength after rolling is due to the joint action of aging strengthening, dislocation and grain boundary strengthening. It is important to improve the mechanical properties of T6 aluminum alloy by accelerating the precipitation rate of the strengthening phase during low temperature aging. After low temperature rolling, T6 aluminum alloy has the highest strength, but the lowest elongation, and the high strength is mainly due to the aging strengthening effect. After low temperature aging, the strength decreased and the elongation did not improve obviously. It was found that the precipitation phase with lower strengthening effect was formed at low temperature aging, and the working hardening ability of aluminum alloy also decreased. The contribution of different strengthening mechanisms to the strength of three states of aluminum alloy during low temperature deformation heat treatment is also discussed in this paper. The results show that with the increase of aging degree of aluminum alloy before low temperature rolling, the aging strengthening effect increases gradually, while the dislocation and grain boundary strengthening effect decreases gradually during low temperature deformation heat treatment.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.21;TG166.3

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