铝—钢异种金属搅拌摩擦焊工艺及性能研究

发布时间：2018-01-16 03:10

本文关键词：铝—钢异种金属搅拌摩擦焊工艺及性能研究　出处：《沈阳理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：铝-钢异种金属的连接在造船、航空、汽车制造等领域具有重要应用,然而由于铝与钢之间物理、化学、力学等性能差异巨大,很难用传统的熔化焊连接。作为一种新型的固相连接技术,搅拌摩擦焊(FSW)在铝-钢异种金属连接中越来越得到广泛关注。本文以汽车制造中常用的5182铝合金与DP1180双相钢薄板(1.2mm厚)为研究对象,系统地研究了铝-钢异种金属FSW对接及搭接工艺,并对接头的微观组织及力学性能做了深入、细致的探讨。主要研究目标为:通过对铝-钢异种金属FSW工艺优化分析,阐明影响接头质量的关键因素,得到与无缺陷、高质量接头;揭示界面金属间化合物(IMC)微观组织特点,阐明界面成形机理,揭示界面微观组织与力学性能之间的关系。主要进行了以下研究工作:选取1.2 mm厚铝-钢薄板进行FSW对接研究,当钢板位于前进侧、铝板位于后退侧时可获得无缺陷的接头,采用搅拌工具偏置,向钢侧偏置1 mm时接头成形性最佳。通过调整转速、焊速两个工艺参数来控制FSW过程中的热输入。当采用转速为400 rpm,焊速为50 mm/min的较低热输入时,可获得与母材等强度、无缺陷、高质量的FSW接头。在此参数下,铝-钢界面处生成一层均匀而连续的IMC薄层,两种材料之间达到良好的冶金结合。利用透射电镜(TEM)对铝-钢FSW对接接头的焊核区及界面处的IMC形貌进行了细致研究,并对Al-Fe反应机理进行了阐述。焊核区能观察到涡旋状洋葱环流动形貌,且不均匀地分布着大小不一的钢颗粒。钢颗粒周围有Al-Fe的IMC生成,经电子衍射谱分析确定为Al5Fe2。铝-钢界面附近分布着许多堆垛层状结构,一定程度上增加了界面IMC层的厚度,降低力学性能。利用TEM进行细致观察发现,Al-Fe界面区由钢侧混合层和厚度大约为250 nm的IMC层组成。混合层呈明暗条带状相间,由约50 nm厚的IMC条带与约500 nm厚的钢母材交替排列组成。IMC层附近存在大量Al的超细晶,钢侧混合层观察到拉长变形的晶粒。电子衍射谱分析表明,对接界面上的Al-Fe IMC为Al5Fe2。选用不同尺寸的搅拌工具,对铝-钢进行FSW搭接,研究了不同搅拌工具尺寸、下压量及热输入对接头组织及性能的影响。将钢板置于下方,铝板置于上方,下压量为压入钢板0.2 mm。采用大尺寸的搅拌工具,当转速为800 rpm,焊速为50mm/min,钢置于前进侧时,获得断在母材与母材等强度的接头。在焊核区界面附近分布着许多剥落在铝基体中的钢颗粒,其周围包裹着很厚的IMC。Hook缺陷明显得到控制减弱,仅在前进侧微小突起,且在界面形成了连续、均匀的IMC层,经EDS成分分析为Al4Fe。
[Abstract]:Aluminum-steel dissimilar metals have important applications in shipbuilding, aviation, automobile manufacturing and so on. However, the physical, chemical and mechanical properties of aluminum and steel vary greatly. It is difficult to connect with traditional fusion welding. As a new solid-state bonding technology. Friction stir welding (FSW) has attracted more and more attention in the connection of aluminum and steel dissimilar metals. In this paper, the thickness of 5182 aluminum alloy and DP1180 dual phase steel sheet is 1.2mm thick, which is commonly used in automobile manufacturing. For the study. The docking and lapping process of aluminum-steel dissimilar metal FSW were systematically studied, and the microstructure and mechanical properties of the joint were also studied. The main research objectives are as follows: through the optimization and analysis of FSW process for Al-steel dissimilar metals, the key factors affecting the quality of joints are clarified, and the joints with no defects and high quality are obtained. The microstructure of intermetallic intermetallic compound (IMC) was revealed and the mechanism of interfacial forming was explained. To reveal the relationship between interface microstructure and mechanical properties. The main work is as follows: 1.2mm thick Al-steel plate is selected for FSW docking, when the plate is located on the forward side. When the aluminum plate is located on the back side, it can obtain the non-defect joint. When the mixing tool is biased and the steel side is biased to 1 mm, the joint has the best formability, and the rotation speed is adjusted. The heat input in FSW process is controlled by two technological parameters of welding speed. When the heat input of 400rpm rotating speed and 50 mm/min welding speed is adopted, the same strength as the base metal can be obtained and there is no defect. High quality FSW joints. Under this parameter, a uniform and continuous IMC layer is formed at the Al-steel interface. Good metallurgical bonding was achieved between the two materials. The morphology of IMC at the nugget and interface of Al-steel FSW butt joint was studied in detail by means of transmission electron microscope (TEM). The mechanism of Al-Fe reaction was described. The flow morphology of vortex onion rings was observed in the nugget zone, and the steel particles of different sizes were distributed unevenly. The IMC of Al-Fe was formed around the steel particles. It is confirmed by electron diffraction analysis that Al _ 5Fe _ 2. There are many stacking layered structures near the Al-steel interface, which increases the thickness of the interface IMC layer to a certain extent. It is found that the Al-Fe interfacial zone is composed of a steel side mixed layer and a IMC layer about 250nm thick. There are a large number of ultrafine grains of Al in the vicinity of the IMC layer, which consists of the alternating arrangement of about 50 nm thick IMC strip and about 500nm thick steel base metal. The elongated grains were observed in the steel side mixed layer. The Al-Fe IMC on the butt interface was Al _ 5Fe _ 2 by electron diffraction spectrum analysis. The mixing tools of different sizes were selected. The effects of different mixing tool size, pressure and heat input on the microstructure and properties of the joint were studied by FSW. The steel plate was placed under the plate and the aluminum plate was placed on the top. The pressure is 0.2 mm. when the speed is 800rpm, the welding speed is 50mm / min, the steel is placed on the forward side. The joints with the same strength as the base metal and the base metal are obtained. There are many steel particles which flake off in the aluminum matrix near the interface of the nuke zone, and the thick IMC.Hook defects around them are obviously controlled and weakened. There are only small protrusions in the forward side, and a continuous and uniform IMC layer is formed at the interface, which is analyzed by EDS as Al _ 4Fe _ 4.
【学位授予单位】：沈阳理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG453.9

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