同轴送粉钢铝对接激光熔钎焊界面层的控制研究

发布时间：2018-05-08 02:26

本文选题：激光对接焊 + 填粉　；参考：《湖南大学》2015年硕士论文

【摘要】：钢铝异种材料焊接结构高强轻质等方面的综合优势使其在汽车制造领域应用越来越广泛,有利于汽车轻量化的发展。但二者物理化学性质差异明显,相互固溶度低,极易生成Fe-Al脆性金属间化合物,严重影响焊接接头的力学性能。因此,钢铝异种合金连接成为焊接领域的难点。本文选取第三代车身用钢TG-1和5251铝合金为研究对象,从焊接工艺参数控制和合金元素作用机制两方面入手,率先运用同轴送粉技术实现钢铝异种材料的激光对接熔钎焊接,开展钢铝激光熔钎焊特性和界面行为研究,利用金相显微镜、扫描电镜、微区X射线衍射、拉伸试验机、纳米压痕等手段系统分析了接头的金相组织、元素分布、界面主要物相、断口形貌和接头力学性能等,以期为实现高质量钢铝异种材料激光熔钎焊接提供理论依据和技术支持。首先,通过填加AlSi12、AlSi5、Al Cu5、Zn Al15合金粉末,分析接头特性,研究不同元素对焊件表面形态、微观界面层结构特征的影响,并评定不同粉末填加下的接头力学性能。优化的工艺参数下,均获得有效的钢铝熔钎焊接连接。Si元素作用下,界面层主要生成Fe_4Al_(13)、FeAl_3Si及Fe_(0.905)Si_(0.0905)等化合物,Fe-Si相及Fe-Al-Si相降低了接头脆性;Cu元素在界面层处未形成Al-Cu及Fe-Al-Cu相,但固溶在析出的Fe_4Al_(13)中,通过降低Fe、Al原子扩散速率影响界面反应;Zn元素固溶在Fe_4Al_(13)中,没有改变Fe-Al相的晶体结构,却改善了其性能。AlSi12合金粉末作用下接头抗拉强度最高,为128.3 MPa,约为铝合金母材强度的68%,说明Si元素含量的增加有利于降低界面层硬度。综合焊缝成形性、界面层的微观组织及接头力学性能,AlSi12粉末作用效果最好。其次,在工艺方面,研究界面层厚度、工艺参数及接头强度之间的关系,寻求金属间界面层相关控制机理。界面层厚度与各工艺参数存在一定联系,需要合理匹配焊接工艺参数,将界面层厚度控制在10μm范围内。接头的抗拉强度与界面层厚度之间虽暂时未发现明显的线性及函数相关性,但有效的钎接接头界面层厚度大部分集中在此范围。接头强度在有效激光功率范围内,呈现先增长后降低的趋势,且随焊接速度的增加而逐渐增大。而在有效间隙范围内,接头强度随对接间隙的增大逐渐降低。论文研究结果对开发异种金属连接新工艺和促进轻量化结构应用具有一定的理论意义和应用价值。
[Abstract]:The comprehensive advantages of steel and aluminum dissimilar materials in welding structure, such as high strength and light weight, make it more and more widely used in the field of automobile manufacturing, which is beneficial to the development of automobile lightweight. However, the physical and chemical properties of the two are obviously different, and the mutual solution is low, so it is easy to form Fe-Al brittle intermetallic compounds, which seriously affects the mechanical properties of welded joints. Therefore, the joint of steel and aluminum dissimilar alloys has become a difficult point in welding field. In this paper, the third generation of body steel TG-1 and 5251 aluminum alloy are selected as the research objects. Starting from the control of welding process parameters and the mechanism of alloy element action, the coaxial powder feeding technology is first used to realize laser butt welding of dissimilar materials of steel and aluminum. The characteristics and interface behavior of laser brazing of steel and aluminum were studied. The metallographic structure and element distribution of the joint were systematically analyzed by means of metallographic microscope, scanning electron microscope, microzone X-ray diffraction, tensile testing machine and nano-indentation. The main interface phase, fracture morphology and mechanical properties of joints are expected to provide theoretical basis and technical support for the realization of laser welding of high quality steel and aluminum dissimilar materials. First of all, by adding AlSi12AlSi5AlSi5AlCu5Cn-Zn Al15 alloy powder, the joint characteristics were analyzed, the effects of different elements on the surface morphology and microstructure of the interface layer were studied, and the mechanical properties of the welded joints were evaluated by adding different powders. Under the optimized technological parameters, under the action of effective steel and aluminum welding joining. Si element, the interface layer mainly produces Fe4AlAl1 / 13Sh / FeAl3Si and Feal 0.905SiP / Fe-Al-Si phases, which reduce the brittleness of the joints. No Al-Cu and Fe-Al-Cu phases have been formed at the interface layer of the interface layer, and the results show that there are no Al-Cu and Fe-Al-Cu phases in the interfacial layer of the interface layer, so that the Fe Si phase and the Fe-Al-Si phase can be reduced by the addition of Fe Si phase and Fe-Al-Si phase in the interface layer. But in the precipitated Fe4AlSi-13), the solid solution of Zn element in the interface reaction by decreasing the diffusion rate of Fenal atoms in the Fe4AlSi-13) did not change the crystal structure of the Fe-Al phase, but improved its properties. The tensile strength of the joints under the action of the powder. AlSi12 was the highest. 128.3 MPA, about 68% of the strength of the aluminum alloy base metal, indicating that the increase of Si content is beneficial to the reduction of the hardness of the interfacial layer. The effect of AlSi12 powder on the microstructure and mechanical properties of the interfacial layer is the best. Secondly, the relationship among intermetallic layer thickness, process parameters and joint strength is studied, and the control mechanism of intermetallic interfacial layer is sought. The thickness of the interfacial layer is related to the process parameters. It is necessary to match the welding parameters reasonably and control the thickness of the interfacial layer in the range of 10 渭 m. Although there is no obvious linear and functional correlation between the tensile strength and the thickness of the interface layer, the effective interfacial layer thickness of the brazing joint is mostly concentrated in this range. In the range of effective laser power, the joint strength increases first and then decreases, and increases gradually with the increase of welding speed. However, in the range of effective clearance, the joint strength decreases with the increase of butt clearance. The results of this paper have certain theoretical significance and application value for developing new technology of dissimilar metal joining and promoting the application of lightweight structure.
【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】：TG457.1

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