【作者】 胡文祥；

【导师】 雷玉成；

【作者基本信息】 江苏大学 ， 材料加工工程， 2010， 硕士

【摘要】 SiC颗粒增强铝基复合材料(简称SiCp/Al基复合材料)具有比强度高、比模量高、膨胀系数低、耐磨性良好等优异的综合性能,在航天、航空结构件、发动机耐热和耐磨部件等方面有着广阔的应用前景。然而由于SiCp/Al基复合材料的特殊组织结构导致其焊接性很差,难以形成高强度焊接接头,成为该种材料走向实用化的严重障碍,因此铝基复合材料的焊接技术是其走向工业化必须解决的问题。本文以SiCp/6061Al MMCs为研究对象,采用添加药芯焊丝的方式对其进行等离子弧(以Ar+N2为离子气、Ar为保护气)焊接。借助于金相显微镜、扫描电镜、X射线衍射分析仪、能谱仪及透射电子显微镜等微观分析手段,研究了不同成分药芯焊丝对焊接接头组织与性能的影响,并对焊接熔池内大片状Al3Ti的形成机理以及细化工艺进行了系统的分析。基于Ti元素在焊接SiCp/6061Al MMCs时的作用,本试验研制了SiCp/6061Al MMCs熔化焊接专用富Ti药芯焊丝。药芯焊丝以其药粉易调节,制作工艺简单等优点,为SiCp/6061Al MMCs的焊接性能的研究提供了有利的条件。本文选用了Ti-Si-Al、Ti-Mg-Al和Ti-Si-Mg-Al三种不同成分的药芯焊丝分别对SiCp/6061Al MMCs进行焊接试验。在填加Ti-Si-Al和Ti-Mg-Al两种药芯焊丝的试验中,焊丝内部Ti元素的成分比例为固定值,通过改变Si和Mg的成分比例,分别对SiCp/6061Al MMCs进行焊接试验,进而分析出Si和Mg对焊缝性能的影响。在对前面试验结果分析的基础上制作Ti-Si-Mg-Al药芯焊丝,对SiCp/6061Al MMCs进行焊接试验,并对试验结果进行分析。试验结果表明填加15Ti-5Si-5Mg-Al药芯焊丝等离子弧焊接SiCp/6061Al MMCs的焊接接头强度最高,其最高值为267Mpa达到母材强度的83.4%。焊接熔池内适当的Ti元素能够抑制脆生相Al4C3的生成,但是过多的Ti元素会导致焊缝内部形成大片状的Al3Ti相,降低焊缝性能。本试验通过对焊缝内部大片状Al3Ti相微观形貌从200倍至50000倍的逐次放大观察,结合对Al3Ti颗粒形成机理的研究,分析得知焊缝内部大片状Al3Ti相是由细小棒状Al3Ti颗粒聚集而成。通过提高熔池液态金属运动的剧烈程度和改善熔池内部合金元素的比例等方式可以抑制细小棒状Al3Ti颗粒的聚集,从而达到消除大片状Al3Ti相,提高焊接接头性能的目的。更多还原

【Abstract】 SiC particle reinforced aluminum metal matrix composites(SiCp/Al MMCs), which exhibit excellent combinations of high specific strength, high specific stiffness, low coefficient of thermal expansion and excellent wear resistance, have more and more widely application in aerospace-flight, aviation structure, and heat resistant wearable parts of engine. However, Aluminum metal matrix composites is not applied widely in industry duo to its poor weldability. The welding technique is the key to wide industry applicaton for Aluminum metal matrix composites.The effects on microstructures and mechanical properties and the alloying mechanism of weld by plasma arc "in-situ" welding (Ar and N2 as ionized gas, Ar as fielded gas) of SiCp/6061Al MMCs filling with flux-cored wires were investgated with the help of OM (optics microscopy), SEM (scanning microscopy), TEM (Transmission electron microscopy), EDS (Energy Disperse Spectroscopy) and XRD (X-ray diffraction) in the present work. A systemic analysis was also carried out on the formation mechanism and refinement technology of the long strip Al3Ti phase.Based on the analysis of the role of Ti in the weld, which can inhibit the harmaful phase and inprove the performance of the weld. The rich-Ti flux-cored wire was produced specialized for welding of SiCp/Al MMCs, which have the advantage of simply producting process and easily adjusting ratio of the powder.Three kind of flux-cored wires were used for the SiCp/Al MMCs welding test, that is Ti-Si-Al, Ti-Mg-Al and Ti-Si-Mg-Al wires. The content of Ti in the Ti-Si-Al and Ti-Mg-Al flux-cored wires is unchanged all the time, so that the role of Si and Mg in the motlen pool can be analyzed by changing the ratio of them repectively in the flux-core wires during welding. The Ti-Si-Mg-Al flux-cored wire was prepared on the base of the research of Si and Mg. The test results show that the highest tensile strength of the weld joints was getting by plasma arc welding of SiCp/Al MMCs with 15Ti-5Si-5Mg-Al flux-cored wire as filler and the maximum value of the joint is 267 MPa up to 83.4% of the base metal.As the formation of long strip Al3Ti phase, the tensile strength of the joint will decreased when too much Ti fusing into the pool, although the need like brittle phase Al4C3 is inhibited. Combined the observation of microstructure with the molding mechanism of Al3Ti particles, we can get the conclusion that the long strip Al3Ti phase in the weld is an aggregates, which is consist of fine Al3Ti particles. The tensile strength of the weld can be improved by suppressing the formation of the long strip Al3Ti phase, while the formation of the long strip Al3Ti phase can be inhibited by increasing the movement of the molten pool or improving the ratio of the alloy elements in the flux-cored wires.更多还原