摘要：拉伸冷作硬化作为冷作硬化的方法之一，随着其技术的优化和发展，如今已经被工程应用大量的使用。但是拉伸过程中试样横截面缩小是无法避免，因此材料的强化能力并没有得到完全的发挥，强化效果受此限制。区别于拉伸冷作硬化，扭转冷作硬化对材料的加工过程中，材料产生的变形十分均匀，因此材料的强化能力得到了最大程度地发挥，其强化效果相较于拉伸冷作硬化更为显著。

本文通过控制试样的单位长度相对扭转角，来控制对铝合金的扭转硬化程度。对原材料和经过不同扭转硬化程度的材料进行拉伸和冲击实验，其中拉伸实验在常温下进行，冲击实验在不同的温度下进行，探究扭转硬化对铝合金的拉伸力学性能（包括抗拉强度，RP0.2，断后伸长率以及断面收缩率）的影响，以及扭转硬化程度和温度对铝合金冲击韧性的影响。

实验结果显示，扭转硬化对实验所选铝合金的强度性能的强化效果有限，试样的单位长度相对扭转角为24°/mm时（实验最大的扭转硬化程度），6061-T6铝合金的RP0.2提高了6.47%，抗拉强度提高了4.01%。与此同时，铝合金的塑性性能却随着扭转硬化程度的增强下降严重，当达到实验最大的扭转硬化程度时，铝合金的断后伸长率下降了79.45%，断面收缩率下降了86.67%。综合两者考虑，扭转硬化对此类高强度、低韧性的铝合金的强化效果不明显。基于实验所得数据，本文建立了6061-T6铝合金拉伸力学性能与其扭转硬化程度的关系函数。

在相同温度条件下，随着扭转硬化程度的增加，铝合金的冲击韧性逐渐降低，在扭转硬化程度较小时，冲击韧性的下降幅度较小；随着扭转硬化程度的增强，铝合金冲击韧性的下降幅度有所提高。在扭转硬化程度相同时，在一定的温度范围内，随着温度的不断降低，铝合金的冲击韧性略有升高。因此，在自然气候条件下，铝合金在使用过程中可忽略温度对其冲击韧性的影响。同时，本文基于实验构建了铝合金冲击韧性在相同温度下与扭转硬化程度的关系函数，以及在相同扭转硬化程度下与温度的关系函数。

关键词：铝合金；扭转硬化；拉伸实验；强度性能；塑性性能；冲击韧性

Abstract：Stretching cold hardening As one of the methods of cold hardening,in pace with its technology optimization and development, has now been used in a mass of engineering applications. However, the cross-section of the specimen during the stretching process can not be avoided, so the material's strengthening ability has not been fully exerted, and the strengthening effect is limited. Compare with the stretching cold hardening, torsional cold work hardening of the material during the processing, the material produced by the deformation is very uniform, so the material to enhance the ability to maximize the play, the strengthening effect is more significant than the tensile hardening.

In this paper, the degree of torsional hardening of aluminum alloy is controlled by controlling the relative twist angle per unit length of the specimen. The  tensile and impact tests were carried out between the raw materials and the materials that with different torsional hardening degrees. The effects of torsional hardening on the tensile mechanical properties (including tensile strength, non - proportional elongation strength, elongation at break and cross-section shrinkage) of aluminum alloy were investigated. The effects of torsional hardening degree and temperature on the impact toughness of aluminum alloy were investigated.

The experimental results show that the torsional hardening effect on the strength of the selected aluminum alloy is limited, and the relative twist angle per unit length  of  the specimen is 24 ° / mm (the maximum degree of torsional hardening), the non-proportional extension of the aluminum alloy Strength increased by 6.47%, and the tensile strength increased by 4.01%. At the same time, the plastic properties of aluminum named 6061-T6 alloy decreased with the increase of torsional hardening degree. When the degree of torsional hardening was reached, the elongation of aluminum named 6061-T6 alloy decreased by 79.45% and the area shrinkage decreased by 86.67%. Above all, torsional hardening does not adapt to the strengthening of such aluminum alloys. In view of the experimental data, the relationship  between  tensile  mechanical  properties   and  torsional   hardening  degree      of aluminum alloy was established.