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摘 要 铝合金和钛合金的复合焊接结构能将这两种合金的良好特性结合到一起，因而在航空、航天以及汽车等工业领域有着广泛的应用。但是 Al、Ti 两种元素之间的物理、化学等性能差异较大，使得在如何焊接两种金属获得良好接头的问题上存在着很大的困难。抑制两种金属焊接过程中生成的金属间化物是 Al、Ti 异种合金焊接过程中的主要问题。 本文采用激光熔钎焊的方法，分别将激光作用在 5mm 厚的 6063铝合金和5mm厚的 Ti3Al2.5V 钛合金上。在焊接过程中，当激光光束作用在铝合金上时，使得铝合金熔化，而钛合金熔点较高仍保持固态， 液态铝合金铺展浸润在固态钛合金表面，实现了 Al/Ti 异种合金的连接。当激光光束作用在熔点较高的钛合金一侧时，通过中间固态钛合金层的热传导使得铝合金熔化，液态的铝合金铺展浸润钛合金表面，得到了高质量的 Al/Ti 异种合金接头。 在试验过程中，通过改变光束偏转角和光束偏移量来控制熔池形状和固体钛层的厚度，从而控制界面中金属间化合物的生成。焊后通过金相显微镜、扫描电镜（SEM）及能谱分析仪（EDS） 、X 射线衍射仪（XRD）等微观分析设备以及电子万能拉伸试验机、显微电子硬度仪等力学性能分析设备对接头性能进行分析。 试验结果表明：当激光作用在钛合金一侧，激光功率 P=4000W，光束偏移量 D 0.8mm≤D≤1.0mm，光束偏转角 θ=5°，焊接速度 V=1.2m/min 时，焊缝的成形较好，并且当光束偏移量 D=0.8mm 时，接头的抗拉强度达到最大值，为 132.8MPa；通过对接头的微观组织进行分析，Al/Ti 异种合金焊缝界面处的金属间化合物主要为AlTi、AlTi3、Al2Ti、Al3Ti。58958
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毕业论文关键词：铝合金，钛合金，激光熔钎焊，焊缝成形，力学性能，组织物相
Abstract The composite welding structure of aluminum alloy and titanium alloy is widely used in the aerospace and automotive industries because of its performance advantage which combine the advantages of both alloys together. However, the base materials of Al and Ti have a great difference in physical and chemical properties and the difference will influence the dissimilar alloy’s welding joints greatly, which will reduce the joint quality seriously. So control the intermetallic compound produced by the reaction of Al/Ti dissimilar alloy welding is the biggest problem of Al/Ti dissimilar alloy welding. This paper uses laser penetration brazing to joining the 6063 aluminum alloy with 5mm thickness and the Ti3Al2.5V titanium alloy with 5mm thickness. During the welding process, when the laser acts on the surface of Al alloy the laser melted a side of the aluminum alloy. Then the liquid aluminum alloy spread on the surface of Ti alloy, forming an effective laser welding brazing welded joints of Ti/Al dissimilar alloy. When the laser acts on the surface of Ti alloy. Al alloy is melted by heat conduction from the middle solid Ti layer. Then the liquid aluminum alloy spread on the surface of Ti alloy form an effective laser welding joints. In the experiment, the shape of the molten pool and the thickness of the middle solid Ti layer in the interface can be controlled by adjusting the beam offset, beam deflection angle. The microstructures in the joint are studied by using Optical Microscopy, scanning electron microscope, EDS and XRD. Joint mechanical property was measured by tensile test and hardness test. The test results show that when the laser acts on the surface of Ti alloy, the process parameters were 4000W of the laser power, 0.8mm to 1.0mm between the laser beam offset, 5°deflection angle of the laser beam and 1.2m/min of the speed of welding, the appearance of weld is perfect. When the laser beam offset is 0.8mm, the joint’s maximum tensile strength is 132.8MPa. From the analysis of the joint’s microscopic structure, intermetallic compounds was likely to be AlTi,AlTi3,Al2Ti and Al3Ti。