新型高强高导Al-Mg-Si-Cu合金性能及其微观结构研究

发布时间：2018-06-08 21:01

本文选题：Al-Mg-Si-Cu合金 + 析出相　；参考：《湖南大学》2015年硕士论文

【摘要】：铝合金是工业中应用最广泛的有色金属结构材料,其比强度高,成型性优良,也具有良好的耐腐蚀性能,因此在汽车、航空和高铁等领域得到了广泛应用。众所周知,纯铝是一种优良的导体,铝的导电性能在常用金属材料中排名第四,但由于纯铝机械强度偏低,使其在电力工程等方面的应用受到限制。当合金化后,材料强度获得一定提升,然而合金化却会使铝的导电性能下降。虽然铝合金作为导电材料已经有所应用,但为了使铝合金作为导电材料或者导热材料在实际工业中得到更为广泛的应用,制造高强高导铝合金成为电力工业以及科学界较为关心的问题。在纯铝中添加少量镁、硅和铜所形成的6xxx系(Al-Mg-Si-Cu)铝合金是人类现代生活中应用最广泛的铝合金。由于镁、硅和铜三种元素添加对铝导电性能的影响较小,并且6xxx系铝合金中合金含量较低,这些综合因素使6xxx系(Al-Mg-Si-Cu)铝合金成为合适的轻量化导电导热材料,尤其是对强度和导电性能提出更高要求时。本课题以形变时效工艺为主线,通过调控形变前合金元素聚集状态以及后续时效工艺,制备新型高强高导Al-Mg-Si-Cu合金。实验选取了2种Al-Mg-Si-Cu合金(合金元素总含量相似,Mg/Si比分别是1和2),两种合金都分别采用传统T6时效工艺和形变时效工艺处理,然后在不同温度(150o C、180o C、210o C和240o C)下进行时效处理。本文主要借助硬度测试、导电率测试和拉伸测试以及透射电子显微镜(TEM)研究不同工艺制备的Al-Mg-Si-Cu合金的性能和微观结构,试图揭示形变时效工艺对Al-Mg-Si-Cu合金综合性能(强度和导电率的结合)改善的机理以及形变量和预处理对Al-Mg-Si-Cu合金综合性能的影响,建立宏观性能与微观结构特征的关系。本文得到的主要结论如下:(1)通过改变传统时效工艺加工顺序,对Al-Mg-Si-Cu合金进行形变时效工艺处理,合金综合性能都获得较大提升。其原因是形变时效工艺通过在后续退火前的形变引入大量位错,位错在后续退火后弥补由于析出相过于粗化而下降的强度,使得强度得以保持。位错本身对材料的导电率几乎没有影响,却可以使析出相显著粗化,从而合金导电率大幅度提升;(2)选择合适的后续时效温度可以优化合金的综合性能,利用人工时效温度可以调控析出相粗化速率以及位错退化速率,使两者恰当结合可以使综合性能最优;(3)在形变时效工艺中,由于自然时效和人工时效预处理在基体内预制的溶质团聚物不同,使得形变过程中引入的位错含量以及位错存在的形式有所不同,因而带来的强化效果不同。后续时效时,在强度接近的情况下,导电率提高程度不同,最终使得综合性能有差别;(4)形变时效工艺中形变量不断增大时,合金综合性能逐渐提高。形变量增加会使基体内预制的位错量以及位错存在的形式不同,从而使得合金综合性能得到不同程度改善。位错的存在不仅为材料提供强化作用,在后续时效过程中,位错也可以作为原子扩散通道,使后续时效时析出规律发生改变。
[Abstract]:Aluminum alloy is the most widely used nonferrous metal structure material in industry. It has high specific strength, good formability and good corrosion resistance. Therefore, it has been widely used in the fields of automobile, aviation and high iron. It is known that pure aluminum is a good conductor. The conductivity of aluminum is fourth in common metal materials. The mechanical strength of pure aluminum is low and its application in power engineering is limited. When alloying, the strength of the material is improved, but alloying will reduce the conductivity of aluminum. Although aluminum alloy has been applied as conductive material, the aluminum alloy is used as conductive material or heat conduction material in actual work. The manufacture of high strength and high conductivity aluminum alloy has become a concern in the power industry and the scientific community. Adding a small amount of magnesium to pure aluminum, 6xxx (Al-Mg-Si-Cu) aluminum alloy formed by silicon and copper is the most widely used aluminum alloy in human modern life. The addition of three elements of magnesium, silicon and copper to aluminum conductance is added to the aluminum alloy. The effect of energy is smaller and the alloy content in 6XXX Al alloy is low. These comprehensive factors make 6xxx (Al-Mg-Si-Cu) aluminum alloy a suitable lightweight conductive and conductive material, especially for the higher requirements of strength and conductivity. The new high strength and high conductivity Al-Mg-Si-Cu alloy was prepared by the subsequent aging process. 2 kinds of Al-Mg-Si-Cu alloys were selected (the total content of the alloy elements was similar, the Mg/Si ratio was 1 and 2 respectively). The two alloys were treated with the traditional T6 aging process and the deformation aging process respectively, and then the aging place was carried out at different temperatures (150O C, 180o C, 210o C and 240o C). In this paper, the properties and microstructure of Al-Mg-Si-Cu alloys prepared by different processes are studied by means of hardness testing, conductivity testing and tensile testing, and transmission electron microscopy (TEM). The mechanism of deformation aging process to improve the comprehensive properties of Al-Mg-Si-Cu alloys (the combination of strength and conductivity), as well as the shape variables and pretreatments are revealed. The relationship between the macroscopic properties and the microstructure characteristics of the Al-Mg-Si-Cu alloy was established. The main conclusions obtained in this paper are as follows: (1) by changing the processing order of the traditional aging process and treating the Al-Mg-Si-Cu alloy by deformable aging process, the comprehensive properties of the alloys have been greatly improved. The reason is that the deformation aging process passes through the process. A large number of dislocation is introduced before the subsequent annealing, and the dislocation is made up to make up the strength of the precipitated phase after the subsequent annealing, which makes the strength keep. The dislocation itself has almost no effect on the conductivity of the material, but can make the precipitated phase coarsely coarsened and the alloy conductivity increased greatly; (2) select the appropriate follow-up time. The effective temperature can optimize the comprehensive properties of the alloy. Using the artificial aging temperature can regulate the precipitate coarsening rate and the dislocation degradation rate, so that the proper combination of the two can make the comprehensive performance optimal. (3) in the deformation aging process, the deformation of the prefabricated solute aggregate in the matrix is different because of the natural aging and artificial aging pretreatment. The content of dislocation and the form of dislocation are different in the process, and the strengthening effect is different. In the case of subsequent aging, the increase of electrical conductivity is different, and the overall performance is different. (4) the comprehensive properties of the alloy gradually increase when the deformation amount is increasing. The increase in the amount of dislocation and dislocation in the matrix makes the overall performance of the alloy improve in varying degrees. The existence of dislocation not only provides a strengthening effect for the material, but the dislocation can also be used as an atomic diffusion channel during the subsequent aging process, which makes the precipitation rule change during the subsequent aging.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.21;TG156.92

【参考文献】