铝合金、钛合金电子束焊接接头组织、性能和焊接性能研究

【作者】 常艳君；

【导师】 董俊慧；

【作者基本信息】 内蒙古工业大学 ， 材料加工工程， 2005， 硕士

【摘要】 轻质合金材料具有比强度高、耐蚀、耐热性能好等特点,在国防、航空、航天工业中广泛应用。但是其可焊性差,加工工艺不佳。轻质合金的高能密度焊接是当今世界焊接工艺研究的热点。因此,研究铝合金、钛合金电子束焊接接头组织和性能及其焊接性能,不仅可以丰富电子束焊接的理论知识,而且对指导实际生产具有重要意义。本研究针对国防工业常用的6061-T6铝合金,采用真空电子束焊接方法,在多种工艺条件下进行了施焊,通过金相分析、力学性能试验、X射线衍射和SEM技术研究了对接接头的显微组织与结构、力学性能和断口形貌特征。另外,通过改变坡口表面焊前清理、焊片除气、预热、重熔以及焊接工艺参数,重点分析研究了铝合金焊缝气孔产生倾向和焊缝裂纹的产生原因,找到了减少铝合金焊缝气孔和避免产生焊缝裂纹的最佳工艺措施。此外,对航天航空常用的TC4钛合金材料的真空电子束焊接接头的显微组织、结构、力学性能和断口形貌特征也进行了研究。取得的主要研究结果为:⒈焊前采用细砂纸磨光,再用丙酮清洗坡口,在焊接工艺参数适宜的情况下,铝焊缝气孔数减少;随着热输入的增加,铝焊缝气孔数减少;预热和重熔不仅可以修饰焊缝表面成形,还可以有效减少铝焊缝的气孔数。⒉预热和重熔使得焊缝区和熔合区的等轴晶和胞状树枝晶比较粗大,Mg2Si相的数量减少,导致了铝合金电子束焊接接头的强度、塑性和硬度降低,但仍然高于钨极氩弧焊焊接接头的强度、塑性和硬度。⒊对接接头添加焊片且随着厚度的增加,铝合金焊接接头的抗裂性较好,焊缝产生的裂纹率显著减小。⒋钛合金电子束焊接接头的焊缝组织是由部分柱状晶和细针状αˊ相组成,近缝区组织为αˊ相和部分α相的混合物,靠近母材热影响区组织为α〞相和部分α相的混合物。⒌钛合金焊接接头抗拉强度接近或略高于基材,并保持较高的塑性和韧性,断裂主要发生在母材处。拉伸断口微观形貌为圆形微坑状的等轴韧窝和沿晶韧窝。更多还原

【Abstract】 The lightweight alloy material applied commonly in national defense, astronautics, aviation industry because it has the characteristics such as high specific tenacity, corrosion resistance, the heat-resisting performance. But its weldability is bad and its processing craft is not good. The high-energy density welding about lightweight alloy is the hotspot of world welding craft research. Therefore, the research on microstructure; mechanical properties and welding properties of electron beam welding joints of the aluminium alloy and titanium alloy not only may enrich the electron-beam welding theory knowledge, but also has important significant meaning to production guiding.In this paper, the microstructure; mechanical properties and fracture appearance characteristic of electron beam welding joints of 6061-T6 aluminum alloy which applied commonly in national defence industry were studied by means of metallography,mechanical test and SEM technology. In addition, Based on Electron beam welding tests of aluminium alloy,this paper emphases on pore tendence of welding zone by altering method of clearing of slope surface before welding; removing gas of welding piece; altering technical parameter; preheating; remelting and reason why there exist crack in welding zone. At the same time, the microstructure; mechanical properties and fracture appearance characteristic of electron beam welding joints of TC4 titanium alloy which applied commonly in aviation industries were studied by means of metallography,mechanical test and SEM technology. The important outcomes are introduced as following:⒈If the welding sample of aluminium alloy under feasible technical parameter are grinded with the thin sandpaper at first, and then cleaned with acetone before welding, the pore number in weld zone is least. The heat-input is higher, the pore number is less. Preheating and remelting not only can modify surface of welding seam of aluminium alloy, but also can decrease pore number in welding seam.⒉The tensile strength; plasticity and hardness in weld zone and heat-affected zone of welding samples of aluminium alloy welded by EBW are by far higher than that welded by TIG although they decrease because equiaxed grains and fir-tree crystal become gross and the number of Mg2Si phase decrease evidently by preheating and remelting.⒊Along with the thickness of welding slice increases, the crack rate reduces更多还原