【作者】 蒋海浪；

【导师】 雷玉成；

【作者基本信息】 江苏大学 ， 材料加工工程， 2009， 硕士

【摘要】 颗粒增强铝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,成为当今金属基复合材料发展与研究的主流。然而由于铝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,成为该种材料走向工业应用的严重障碍,因此有必要系统地研究铝基复合材料焊接性。本课题以SiCp/6061A1基复合材料为研究对象,以Ar+N₂为离子气,Ar气为保护气,采用等离子弧焊接方法对其焊接工艺及合金化机理进行了系统的研究。利用金相显微镜、扫描电镜及X射线衍射分析仪等微观分析手段研究了复合材料等离子弧焊接接头微观组织及成分变化,利用硬度试验和拉伸试验研究了等离子弧焊接接头的力学性能。研究表明填加Al-Si-Ti-Ni合金对SiCp/Al基复合材料进行等离子弧原位焊接,填加材料中Ti含量为5%时,可以有效抑制有害相Al₄C₃的生成,得到的焊缝组织较为致密,没有气孔、微观裂纹等缺陷,接头强度较之不加填充材料时有较大提高,达到226MPa,提高了接头的力学性能。研究了使用Al-Si-Ti-Y合金片为填充材料对SiCp/6061A1基复合材料进行等离子弧原位焊接时,焊缝组织和性能的变化。试验表明以Al-Si-Ti-Y合金片为填充材料时,可以细化晶粒获得致密的焊缝组织。在抑制有害相Al₄C₃的生成的同时,接头强度又有较大提高,达到240MPa,有效提高了接头的力学性能。此外还分析了Y对焊缝组织及接头力学性能的影响,研究表明在铝基复合材料焊接过程中添加稀土金属Y,可改善焊缝组织,提高焊缝强度、塑性和韧性。对SiCp/Al基复合材料等离子弧原位焊接接头进行热处理后发现,热处理的最佳工艺为T6 500℃固溶+时效。热处理后焊缝组织状况得到良好的改善,粗大的Al₃Ti相变为短小棒状,消除了晶间偏析,组织更加均匀。热影响区组织中晶粒均得到比较明显的细化,比较接近母材晶粒的大小。焊接接头强度较未热处理时有了较大提高,达到255MPa,而且接头热影响区硬度基本恢复到母材水平。更多还原

【Abstract】 Particle reinforced aluminum metal matrix coMPosites（AI MMCs）,which exhibit excellent combinations of high specific strength,high specific stiffness,low coefficient of thermal expansion and excellent wear resistance,have wide application in aerospace-flight,aviation structure,and heat resistant-wearable parts of engine,and thus represent the mainstream of conteMPorary research and development of metal matrix coMPosites.However,the special microstructure of Al MMCs,which lead to the poor weldability and the difficulty in obtaining high strength welded joint,severely hinder the application of the coMPosites in welded construction.Therefore,a systematic study on the weldability of aluminum matrix coMPosites is imminent.In this paper,SiCp/Al MMCs were selected as research objects,and process and mechanism of SiCp/6061Al MMCs by plasma arc welding（Ar and N2 as ionized gas, Ar as fielded gas） were systematically studied.OM（optics microscopy）,SEM（scanning microscopy） and XRD（X-ray diffraction） were used to observe the microstructure and changing of coMPositions of fusion welded joints of coMPosites.Mechanical properties of fusion welded joints were measured by microhardness and tensile tests.CoMPact microstructure without phases of Al₄C₃ was obtained by plasma arc "in-situ" welding of SiCp/6061Al MMCs with Al-Si-Ti-Ni alloy filler,whose mass fraction of titanium is 5%.And no defects of pores,fissures and incoMPlete fusion is observed in the central zone of weld.The mechanical properties of weld joint were thus iMProved and the tensile strengths of weld joint reach 226MPa.The test results of mechanical property show that the maximum tensile strength of welded joint gained with Al-Si-Ti-Y alloy as filled coMPosite is 240MPa.the microstractures and mechanical properties of the welding joint were researched analysis by plasma Arc "in-situ" welding of SiCp/6061Al MMCs with Al-Si-Ti-Y alloy fillers.The grains were refined and dense microstractures were gained.In addition,the effects of yttrium element on microstructures and factors influence the mechanical properties were also investigated.The result shows that the rare earth element yttrium can iMprove the strength,plasticity and toughness.The microstractures of weld can be ameliorated,too. The results show that the optimum heat treatment process of the weld joint by plasma Arc "in-situ" welding of SiCp/6061Al MMCs is T6 500℃solution and aging. The microstructure of heat treated weld was well iMProved with the size of massive bulky phases Al₃Ti turning into short rod-like,intergranular segregation eliminated and more homogeneous particles.The grains of heat affected zone were refined during the heat treatment,and were the same as that of base material.Thus the tensile strength of joint was heightened to 255 MPa,and the hardness of the the heat affected zone recovered to the pre-welding value.更多还原