合金元素对7000系铝合金淬透性的影响及Mn、Mg、Zn对超高强轧制铝合金组织性能的影响

发布时间：2018-07-10 04:14

本文选题：7000系轧制材铝合金 + 淬透性　；参考：《江苏大学》2017年硕士论文

【摘要】：超高强铝合金一直是航空业研究的重点材料,随着大型化飞机的迅速发展,铝合金已经成为飞机上许多关键零部件的重要材料。然而铝合金的强度和淬透性成为限制其发展的关键因素,如何调控好合金元素的配比是熔炼出综合性能良好的超高强铝合金的关键步骤。本文自行设计熔炼了9种7000系超高强轧制材铝合金,研究了影响7000系铝合金淬透性的因素。研究了主合金元素Zn、Mg及微量元素Mn的变化对7000系轧制铝合金组织与性能的影响。通过对合金进行金相观察、XRD与EBSD分析研究了其微观组织,通过硬度、电导率、拉伸性能等测试及晶间与剥落腐蚀试验研究了其力学性能和抗腐蚀性能。本文主要研究工作所取得的结论如下:(1)通过研究了8种不同7000系铝合金的淬透性规律,使用SEM进行微观组织分析,发现淬透性较差的合金在其远离淬火端会出现含Zr量高的絮状析出物,发现Zr元素是降低合金淬透性的原因。通过分析不同合金的主合金元素原子半径差总和、微量元素Zr和Mn、杂质元素Fe和Si。结果发现:原子半径差总和越小,合金的淬透性越好;微量元素Zr和Mn都降低合金的淬透性,而且Mn的影响程度比Zr大;杂质元素Fe和Si也会降低合金的淬透性。且当主合金元素原子半径差总和较小,合金中杂质元素含量(Fe和Si)也较低时,可以容纳较高含量的Zr元素而保持较高的淬透性;当Zr和杂质元素Fe、Si含量较低时,即使原子半径差总和比较大,也能保持较高的淬透性。(2)研究了Mn元素对7000系轧制材铝合金Al-9.94Zn-2.35Mg-2.53Cu-xMn-0.25Zr组织与性能的影响。结果表明:在Zr含量为0.25%时,添加0.41%的Mn元素能够明显抑制再结晶和晶粒长大,并在后续的固溶时效过程中能够较好的保留位错和小角度晶界,对合金有一定的强化效果。添加Mn元素后,合金在T6时效下强度比不含Mn元素的合金有所提升,从598.5 MPa提升到617.6 MPa,但经过T76时效后强度下降明显,从617.6 MPa降低到566.4 MPa,降低了8.3%,发现Mn元素能减少合金过时效的时间,不利于合金在T76过时效下强度的发挥。Mn元素会降低了轧制材铝合金抗剥落腐蚀性能,能提升抗晶间腐蚀性能。(3)研究了Mg元素及微量Mn元素对超高强轧制材铝合金Al-9.1Zn-xMg-2.72Cu-xMn-0.26Zr组织与性能的影响。结果表明:Mg元素具有促进再结晶的作用,Mg含量提高会导致合金再结晶程度增高,晶粒长大,晶粒等轴性改善,但再结晶过程消耗了较多的位错和低角度晶界,使合金强度有所降低;Mg元素提高会降低合金的抗晶间腐蚀性能,能够提高轧制材铝合金抗剥落腐蚀性能。复合添加0.41 Mn+0.25 Zr能够抑制再结晶和晶粒长大,复合添加0.2 Mn+0.25 Zr不能抑制再结晶,但可以抑制晶粒长大。开发了性能优异的7000系铝合金,其合金成分为Al-8.94Zn-2.55Mg-2.63Cu-0.26Zr,在T76时效下强度达到628.9MPa,延伸率为7.3%,抗剥落腐蚀等级达到PB级。(4)研究了Zn元素对超高强轧制材铝合金Al-xZn-2.62Mg-1.29Cu-2.0Zr组织与性能的影响。结果表明:Zn元素具有促进再结晶的作用,Zr元素对再结晶有抑制作用,当Zn/Mg值超过3.61时,合金中Zn元素提高不能增加合金中时效沉淀强化相,合金的强度反而有所降低,Zn含量越高,合金的抗晶间腐蚀性能越差,对抗剥落腐蚀性能影响不大。本实验开发了抗拉强度达到682.2 MPa的超高强铝合金,其合金成分为Al-9.79Zn-2.71Mg-1.27Cu-0.15Zr,在T6时效下抗拉强度达到682.2 MPa,延伸率为6.2%,T76时效下抗拉强度也达到630.1 MPa,延伸率为7.76%,硬度也分别为226.9 HV和207.8 HV,T76时效下其抗晶间腐蚀性能达到3级,抗剥落腐蚀性能为PC级,单端淬透性也达到80mm,综合性能优异。
[Abstract]:Super high strength aluminum alloy has always been the key material in the research of aviation industry. With the rapid development of large-scale aircraft, aluminum alloy has become an important material for many key parts of the aircraft. However, the strength and hardenability of aluminum alloy have become the key factor to limit its development. How to regulate the ratio of alloy elements is a good melting process. The key step of super high strength aluminum alloy is to melt 9 kinds of 7000 series super high strength rolled aluminum alloy. The factors affecting the hardenability of 7000 series aluminum alloy were studied. The influence of the changes of the main alloy elements Zn, Mg and trace element Mn on the microstructure and properties of the 7000 series aluminum alloy were studied. The alloy was observed by metallographic examination, XRD The microstructures of the microstructures were studied by EBSD analysis. The mechanical properties and corrosion resistance were studied through the tests of hardness, conductivity, tensile properties and intergranular and exfoliation corrosion tests. The main conclusions of this paper are as follows: (1) the hardenability of 8 different 7000 series aluminum alloys was studied, and the microstructure of the alloy was made by SEM. It is found that the alloy with high Zr content will appear at the far away from the quenching end. It is found that the Zr element is the cause of reducing the hardenability of the alloy. By analyzing the sum of the atomic radius difference of the main alloy elements, the trace elements Zr and Mn, the impurity elements Fe and Si., the results of the impurity elements Fe and Si. are found: the smaller the atomic radius difference, the quenching of the alloy. The better permeability is, the microelements Zr and Mn both reduce the hardenability of the alloy, and the effect of Mn is greater than that of Zr; the impurity elements Fe and Si also reduce the hardenability of the alloy. And when the sum of the atomic radius difference of the main alloy elements is smaller and the content of the impurity elements (Fe and Si) in the alloy is also low, it can hold a higher content of the Zr element to maintain a higher quenching. When the content of Zr and impurity elements Fe and Si is low, even if the sum of the atomic radius difference is larger, it can also maintain a higher hardenability. (2) the effect of the Mn element on the microstructure and properties of the aluminum alloy Al-9.94Zn-2.35Mg-2.53Cu-xMn-0.25Zr of the 7000 series rolling material is investigated. The results show that the addition of 0.41% Mn elements can be significantly inhibited when the content of Zr is 0.25%. When the crystallization and grain grow up, the dislocation and small angle grain boundary can be retained in the subsequent solution and aging process. The alloy has a certain strengthening effect on the alloy. After adding Mn element, the strength of the alloy in T6 aging is higher than that of the alloy without Mn element, from 598.5 MPa to 617.6 MPa, but the strength decreases obviously after aging after T76, from 617.. 6 MPa decreased to 566.4 MPa and decreased by 8.3%. It was found that the Mn element could reduce the time of over aging of the alloy, and it was not conducive to the strength of the alloy under T76 over aging. The.Mn element could reduce the corrosion resistance and enhance the intergranular corrosion resistance of the rolled aluminum alloy. (3) the Mg element and the trace Mn element were studied for the ultra-high strength rolled aluminum alloy Al-9.1. The effect of Zn-xMg-2.72Cu-xMn-0.26Zr on the microstructure and properties shows that the Mg element has the effect of promoting recrystallization. The increase of Mg content will lead to the increase of the recrystallization degree of the alloy, the grain growth and the equiaxed grain of the grain, but the recrystallization process consumes more dislocation and low angle crystal boundary, which reduces the strength of the alloy, and the increase of the Mg element will decrease. The anti exfoliation corrosion resistance of the alloy can be improved by the anti crystal corrosion resistance of the alloy. Adding 0.41 Mn+0.25 Zr can inhibit recrystallization and grain growth. Adding 0.2 Mn+0.25 Zr can not inhibit recrystallization, but the grain growth can be inhibited. A 7000 series aluminum alloy with excellent performance is developed, and its alloy composition is Al-8.94Zn-2.55Mg- 2.63Cu-0.26Zr, the strength of T76 is 628.9MPa, the elongation is 7.3%, the anti peeling corrosion grade reaches PB grade. (4) the effect of Zn element on the microstructure and properties of ultra-high strength rolled aluminum alloy Al-xZn-2.62Mg-1.29Cu-2.0Zr is studied. The results show that the Zn element has the effect of promoting recrystallization, Zr elements have inhibition effect on recrystallization, when Zn/Mg When the value is more than 3.61, the increase of Zn element in the alloy can not increase the aging precipitation strengthening phase in the alloy, but the strength of the alloy decreases. The higher the Zn content, the worse the intercrystalline corrosion resistance of the alloy, the less influence on the exfoliation corrosion resistance. This experiment developed a super high strength aluminum alloy with a tensile strength of 682.2 MPa, and its alloy composition is Al-9.79Z N-2.71Mg-1.27Cu-0.15Zr, the tensile strength of the T6 is 682.2 MPa, the elongation is 6.2%, the tensile strength of the T76 is 630.1 MPa, the elongation is 7.76%, the hardness is 226.9 HV and 207.8 HV respectively. The anti crystal corrosion resistance of T76 is 3, the anti peeling corrosion resistance is PC, the single end quenching is also 80mm, and the comprehensive properties are also achieved. Excellent.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG339

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