铝硅合金的搅拌摩擦加工及连接研究

发布时间：2018-05-08 08:54

本文选题：Al-20Si合金 + 搅拌摩擦加工　；参考：《合肥工业大学》2017年硕士论文

【摘要】：铝硅合金由于具有质量轻、热膨胀系数低、耐磨性和抗腐蚀性好等优异的性能而被广泛应用于汽车、航空航天、电子封装等工业领域,其中Al-20Si主要应用于汽车活塞的生产中。然而,过共晶铝硅合金中存在大量的粗大初生硅颗粒和细长针状的共晶硅颗粒,且分布不均匀,降低了材料的组织和性能及连接性,阻碍了其进一步发展和应用。本文分别采用搅拌摩擦加工及焊接的方法对Al-20Si材料进行了二次加工及连接的研究。课题以纯铝和纯硅铸造所得的Al-20Si合金为试验材料,分别探究了搅拌头的形状、搅拌参数及搅拌道次对搅拌摩擦加工效果的影响。结果表明:圆柱带螺纹形的搅拌头可以使材料在搅拌过程具有更好的流动性,对材料的磨削作用更强,且搅拌区域较大,因而比圆锥带螺纹形和方形搅拌头的搅拌效果更好;搅拌摩擦热输入量(转速/加工速度)过大时材料软化严重,搅拌头对材料磨削作用减弱,难以充分细化硅颗粒,而热输入量过小时材料流动性差,硅颗粒难以分布均匀,在950 rpm,47.5mm/min的参数条件下,可以获得最佳的组织状态和力学性能;随着搅拌道次的增加,硅颗粒细化越来越明显,分布越来越均匀,当搅拌道次达到三道时,铸造Al-20Si材料的组织和性能已达到最佳状态,搅拌道次继续增加时,硅颗粒难以进一步细化,分布情况也无明显改变,因而其力学性能无法继续获得明显提高;搅拌摩擦焊接的方法可以避免熔化焊过程所产生的气孔、热裂纹等缺陷,形成具有良好表面成型和组织状态的焊缝组织,焊缝区的抗拉强度和延伸率较母材分别提高43.22%和143.27%。
[Abstract]:Al-Si alloys are widely used in automotive, aerospace, electronic packaging and other industries due to their light weight, low coefficient of thermal expansion, wear resistance and corrosion resistance. Among them, Al-20Si is mainly used in the production of automotive pistons. However, there are a large number of coarse primary silicon particles and slender needle-shaped eutectic silicon particles in hypereutectic Al-Si alloys, and their distribution is uneven, which reduces the microstructure, properties and connectivity of the materials, and hinders their further development and application. In this paper, friction stir machining and welding are used to study the secondary processing and bonding of Al-20Si materials. Using pure aluminum and pure silicon cast Al-20Si alloy as experimental materials, the effects of stirring head shape, stirring parameters and stirring passage on the friction stir processing effect were studied respectively. The results show that the cylinder with threaded head can make the material have better fluidity in the stirring process, the grinding effect on the material is stronger, and the stirring area is larger, so the mixing effect is better than that of the cone with thread shape and the square stirring head. When the friction heat input (rotational speed / processing speed) is too large, the material softens seriously, and the grinding effect of the stirring head on the material is weakened, so it is difficult to refine the silicon particles fully, but when the heat input is too small, the material fluidity is poor, and the silicon particles are difficult to distribute evenly. The optimum microstructure and mechanical properties can be obtained under the parameters of 950 rpm 47.5 mm / min. With the increase of stirring pass, the grain size of silicon becomes more and more obvious and the distribution is more and more uniform. The microstructure and properties of cast Al-20Si materials have reached the best state. When the stirring pass continues to increase, the silicon particles are difficult to be further refined and the distribution has no obvious change, so the mechanical properties can not be further improved. The method of friction stir welding can avoid the defects such as porosity, hot crack and so on, and form the weld structure with good surface forming and microstructure. The tensile strength and elongation of the weld zone are increased by 43.22% and 143.27% respectively compared with the base metal.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG453.9

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