合金化及热处理对7075铝合金组织和应力腐蚀性能的影响

发布时间：2018-05-08 12:23

本文选题：Sc + Ti　；参考：《郑州大学》2017年硕士论文

【摘要】：本研究采用铸锭冶金法制备了含Sc量为0.22%(质量分数,下同)的7075合金和含Ti量为0.18%的7075合金,在含Ti量为0.18%的基础上,制备了含Zn量为11.2%的7075合金,研究了Sc的添加、Ti的添加、Zn的含量对不同时效状态下7075合金的性能的影响,尤其是抗应力腐蚀性能的影响。最后,又重点研究了回归再时效热处理对高Zn含量0.18%Ti7075铝合金的性能影响,得出了综合性能良好的热处理工艺参数。并使用光学显微镜、扫描电子显微镜等手段对不同成分和热处理条件下合金的微观组织的变化进行了研究。结果表明:(1)加入0.22%Sc元素,可以有效细化常规7075铝合金的晶粒,改善合金的晶界。与常规7075相比,0.22%Sc7075合金在T6,RRA,T73和ORRA状态下,硬度分别提高22.9%,29.5%,24.8%和21.5%,抗拉强度分别提高5.77%,6.32%,3.17%和2.4%,延伸率分别提高17.39%,20.59%,12.94%和9.6%,应力腐蚀敏感性因子分别降低了30.28%,26.09%,33.87%和4.41%。(2)加入0.18%Ti元素,可以在一定程度上细化常规7075铝合金的晶粒,改善合金的晶界,降低晶界成分偏析。与常规7075相比,0.18%Ti%7075合金在T6,RRA,T73和ORRA状态下,硬度分别提高11.2%,19.6%,15.2%和12.9%,抗拉强度分别提高2.3%,3.2%,1.4%和3.2%,延伸率分别提高10.1%,18.9%,5.9%和7.2%,对应的应力腐蚀敏感性因子分别降低39.5%,55.2%,51.2%,38.1%。(3)Zn含量提高到11.2%之后,可以降低晶内成分偏析,净化晶界,提高MgZn2的时效强化性能。与0.18%Ti7075相比,高Zn含Ti7075合金在T6,RRA,T73和ORRA状态下,硬度分别提升了29.2%,17.2%,21.3%和16.3%,抗拉强度分别提高9.4%,13.4%,7.0%和6.2%,延伸率分别降低了15.8%,29.5%,6.7%和1.1%,应力腐蚀敏感性因子分别增加了111.4%,47.8%,42.9%和54.1%。(4)对于高Zn含量的7075合金而言,当回归温度为180°C时,随着回归时间的延长,合金的硬度下降,强度下降,抗应力腐蚀性能显著提高;当回归温度为210°C时,随着回归时间的延长,合金的硬度下降,强度在短时间增大到最大值然后下降,抗应力腐蚀性能显著提高。(5)比较本论文所有的研究结果可知,当回归温度为180°C,回归时间为1800s时,高Zn含Ti7075合金的强度高达647MPa,比RRA处理7075合金提高13.51%,应力腐蚀敏感性因子仅为8.34%,比RRA处理7075合金降低70.53%,综合性能性价比最佳。
[Abstract]:In this study, the ingot metallurgy method was used to prepare 7075 alloy with Sc 0.22% (mass fraction, the same below) and 7075 alloy with Ti content 0.18%. On the basis of Ti content of 0.18%, 7075 alloy containing 11.2% Zn was prepared. The effects of Sc addition, Ti addition, and Zn content on the properties of 7075 alloy under different aging conditions were investigated, especially the effect of the content of Zn on the properties of 7075 alloys. In the end, the effect of re aging heat treatment on the properties of 0.18%Ti7075 aluminum alloy with high Zn content was studied, and the heat treatment parameters of good comprehensive properties were obtained. The microstructure of the alloy under different fraction and heat treatment conditions was studied by means of optical microscope and scanning electron microscope. The results show that: (1) adding the 0.22%Sc element can effectively refine the grain of the conventional 7075 aluminum alloy and improve the grain boundary of the alloy. Compared with the conventional 7075, the hardness of 0.22%Sc7075 alloy increases by 22.9%, 29.5%, 24.8% and 21.5% in T6, RRA, T73 and ORRA respectively, and the tensile strength is increased by 5.77%, 6.32%, 3.17% and 2.4% respectively. Do not increase 17.39%, 20.59%, 12.94% and 9.6%. The stress corrosion sensitivity factors are reduced by 30.28%, 26.09%, 33.87% and 4.41%. (2). The grain boundary of the normal 7075 aluminum alloy can be refined to a certain extent, the grain boundary of the alloy is improved, and the segregation of the grain boundary is reduced. Compared with the conventional 7075, the 0.18%Ti%7075 alloys are in the T6, RRA, T73 and ORRA forms. The hardness increased by 11.2%, 19.6%, 15.2% and 12.9% respectively, and the tensile strength increased by 2.3%, 3.2%, 1.4% and 3.2% respectively, and the elongation increased by 10.1%, 18.9%, 5.9% and 7.2% respectively. The corresponding stress corrosion sensitivity factors reduced 39.5%, 55.2%, and 38.1%., which could reduce the segregation of intragranular components, purify the grain boundary, and improve the MgZ. The aging enhancement performance of N2. Compared with 0.18%Ti7075, the hardness of high Zn containing Ti7075 alloy increased by 29.2%, 17.2%, 21.3% and 16.3% respectively in T6, RRA, T73 and ORRA, and the tensile strength increased by 9.4%, 13.4%, 7% and 6.2% respectively, and the elongation decreased by 15.8%, 29.5%, 6.7% and 1.1% respectively, and the stress corrosion sensitivity factor increased respectively, 111.4%, 47.8%, respectively. And 54.1%. (4) for high Zn content of the alloy, when the regression temperature is 180 C, with the extension of the regression time, the hardness of the alloy decreases, the strength decreases and the resistance to stress corrosion increases significantly. When the regression temperature is 210 C, the hardness of the alloy decreases with the extension of the regression time, and the strength is increased to the maximum at a short time. The resistance to stress corrosion is greatly improved. (5) compared with all the research results of this paper, when the regression temperature is 180 C and the regression time is 1800s, the strength of the high Zn containing Ti7075 alloy is as high as 647MPa, which is 13.51% higher than that of the RRA treatment 7075 alloy, and the stress corrosion sensitivity factor is only 8.34%, which is 70.53% lower than that of the RRA treatment 7075 alloy. The price is best.

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG166.3

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