QCr0.8/TC4薄板电子束焊接头组织及断裂路径

对QCr0.8/TC4异种材料薄板进行了电子束对接焊接试验.采用光学金相、扫描电镜、能谱分析及X射线衍射相分析等方法,对接头组织结构及相组成进行了分析.并对接头进行了性能测试及断口形貌观察,分析了断裂性质,探讨了断裂路径.结果表明,焊缝由大量的γ-CuTi相、金属间化合物CuTi2,CuTi3及少量的铜基固溶体组成,且靠近铜合金侧存在一层20 μm左右的反应层,推测其可能为Ti2Cu,CuTi,Cu4Ti3,Cu2Ti,Cu3Ti等多种金属间化合物混合层;QCr0.8/TC4的电子束对中焊接性较差,接头断裂发生在焊缝中心的粗晶区,呈明显的解理断裂特征,接头抗拉强度很低,仅为82.1 MPa.     

电弧作用下熔透型TIG熔池液面行为的数值模拟

在正面熔化半径RZ和板厚h一定的条件下,基于对有电弧作用的熔透型TIG焊接熔池三维液面行为的分析,获得了不同背面熔化半径RB的熔池三维形状模型,利用有限元分析软件surface evolver进行数值模拟,研究了电弧对熔透型TIG焊接熔池液面的影响.结果表明,电弧的作用与否对熔池下液面的大小和形状无显著的影响;在背面熔化尺寸较小时(RB≤2.5 mm附近),电弧对上液面特征量有较大作用;电弧的作用从整体上是使熔池上液面压低.在从脉冲基值过渡到脉冲峰值期间,电弧电压(或弧光光强)增加的部分是由电流增加和熔池上液面被压低两部分引起的.     

Microstructure and mechanical properties of butt joints of QCr0.8／1Cr21NiSTi equal-thickness dissimilar materials by electron beam welding

Butt joints of QCrO. 8/1Cr2lNiSTi equal-thickness dissimilar materials were obtained by electron beam welding with fixed accelerating voltage 60 kV and focus current 1.99 A, changed electron beam current and welding velocity. Microstructure and composition of the EBW joint were investigated by means of optical micrography and EDX analysis, mechanical properties of the joint were also tested. The results show that joint‘ s macrostructure was divided into three zones : top weld zone near QCrO. 8 and bottom weld zone consisting of Cu (ss. Fe ) with a certain amount of dispersedly distributed (α ε) mixed microstructure , middle weld zone consisting of (α ε ) microstracture with a small amount of Cu (ss. Fe )particles. Morphological inhomogeneous macrostructure and uneven chemical compostion of QCrO. 8/1Cr21NiSTi joint by EBW are the most important factor to result in decreasing joining strength.     

大厚度TC21钛合金电子束焊接试验

对56mm厚TC21钛合金进行了电子束对接试验,对接头显微组织和力学性能进行了研究.结果表明,接头焊缝区组织形态以柱状β晶粒为基体,针状的马氏体弥散其中;热影响区从焊缝到母材分为三个区域,依次为等轴再结晶β晶粒区、片状和针状а相形成的魏氏组织区以及片状α相聚集长大的区域;熔合区内柱状晶与等轴晶联生.接头强度达到母材水平,断裂发生在母材内,接头厚度方向性能一致.接头塑性损失较大,只达到母材的50%左右.接头焊缝区硬度最高,其次是热影响区的等轴晶区和魏氏组织区,而热影响区内片状α相聚集长大的区域硬度值最低.

Abstract：

Electron beam welding of TC21 56 mm titanium alloy was carried out. The microstructure and the mechanical properties of welded joints were analyzed and tested. The results showed that the weld zone consisted of the columnar β gains, and in which the transgranular acicular α' martensite were dispersedly distributed. HAZ can be divided into three parts from base metal to weld zone, which are the equiaxed recrystallized β grain zone, Widmanstaten structure zone formed by lamellar and aeicular α phases and lamellar a phase coarsening zone. Fusion zone consists of the adnate columnar and equiaxed grains. Tensile strength of joints reaches to that of base metal and the failure appears in the base metal. The mechanical properties are uniform along the vertical direction. Plasticity in the welded joint is greatly decreased and only up to 50% of that of the base metal. The microhardness in weld zone is the highest, and that of the equiaxed grain zone and Widmanstaten structure zone in HAZ is higher, and the microhardness in columnar a phase coarsening zone is the lowest.     

高温钛合金Ti55/Ti60真空电子束焊接

对 Ti55 与 Ti60 合金薄板进行了电子束焊接,研究了电子束焊接工艺参数对接头组织及力学性能的影响.结果表明,焊缝区形成大量针片状的α' 马氏体,焊缝中心为粗大的柱状晶.焊接工艺参数对焊缝组织和接头抗拉强度有一定影响,接头室温抗拉强度高于母材,600℃时接头抗拉强度与 Ti60 母材相当,抗弯强度达到母材的 80% 左右,冲击韧度能够达到母材的 90% 以上,断裂发生在热影响区处,为韧性断裂.

Abstract：

Ti55 and Ti60 titanium alloy sheets were welded by electron beam, and the influences of parameters on microstmcture and mechanical properties of welding joints were studied. The results show that weld zone is characterized by acicular α' martensite plate,and weld center is formed by coarse columnar crystals. Welding parameters can affect microstructure and tensile strength to a certain extent. At room temperature, the tensile strength of joint is higher than that of base metal. At a higher temperature of 600 ℃, tensile strength of joint is about equal to that of Ti60, and bending strength can be up to 80% of that of base metal, even impact toughness also can be larger than 90% of base metal. Failure occurs in heat-affected zone, and the fracture mode shows toughness characteristic.     

Experimental study of electron beam welded titanium alloy to chromium bronze joint with a vanadium sheet

Electron beam welding experiment of titanium alloy to chromium bronze with a vanadium filler metal was carried out. Microstructure of the joint was observed by optical microscopy and scanning electron microscopy. Tensile strength of the joint was evaluated. The fracture surface of the joint was also analyzed. The results showed that the addition of vanadium filler metal reduced the brittleness of joint by increasing the amount of vanadium-based solid solution in the weld. But the melting point of vanadium.filler metal was so high that large heat input was needed to completely melt the filler metal. Thus, a large amount of interfacial compounds were produced. The tensile strength of joint was 280 MPa with a brittle fracture mode.     

Ti3Al金属间化合物电子束深熔焊接过程数值模拟

基于有限元法，采用改进的双椭球热源模型，对电子束深熔焊接Ti3Al过程进行了移动热源条件下准稳态三维温度场的数值模拟。该模型复合了熔深与电子束参数及材料性质的关系，考虑了对流和辐射散热、相变潜热、材料热物理性能参量随温度的变化以及液态金属的对流传热。通过比较熔深、熔宽的计算值和实际测量值，验证了该模型在电子束焊接温度场模拟中的适用性。     

铜/钛合金电子束焊接工艺优化

研究了QCr0.8/TC4电子束焊接工艺及接头组织,由于铜合金热导率高而熔化量较小,以及焊缝中生成大量脆性金属间化合物相,因此对中焊时接头强度较低.采用偏铜侧进行非对中电子束焊接,接头抗拉强度随偏束量的增大而增高,偏束量为0.8mm时接头最高抗拉强度为270.5MPa.断裂发生在TC4侧熔合线处,为脆性准解理断裂特征.偏铜焊时接头成形得到改善,焊缝包括熔合区及TC4侧反应层两部分.熔合区主要由铜基固溶体组成,硬度较TC4母材有所降低.反应层成分过渡较大,含有多种金属间化合物相.随着工艺参数的变化,反应层厚度也发生变化,从而对接头性能产生影响.     

Effect of Al 2 O3 film on weld appearance of stationary electron beam welded aluminum

Aluminum specimens with and without chemically cleaning were welded by electron beam to investigate the effect of、Al ₂ O₃ film on weld appearance. The removal mechanism of Al ₂ O₃ film during vacuum electron beam welding of aluminum was analyzed and the effect of Al ₂ O₃ film on molten pool flow behavior and weld appearance was investigated. The results showed that the weld width of the specimen was enlarged by chemically cleaning. The solid Al ₂ O₃ film transformed into gaseous Al ₂ O via the reaction with liquid aluminum at the temperature higher than 1 350 K was the main reason for the removal of the film. The weld width was narrowed down by the oxide film due to the inhibition of outward flow driven by the surface tension gradient and the drag force between the Al ₂ O₃ film and liquid Al. The weld penetration was reduced in the initial stage and then enhanced in the metastable stage.     

镍基高温合金电子束钎焊接头界面组织及力学性能

采用Bnp27钎料实现了K465镍基高温合金的真空电子束钎焊.分析了不同工艺参数对接头抗剪强度的影响,借助扫描电镜(SEM)、能谱分析(EDS)和相图分析等方法研究了界面结构,确定了界面反应产物及其形态分布.结果表明,在界面反应层中生成五种产物:大量的镍基γ固溶体和(γ' γ)共晶相,大量的富含钨的Ni3B和CrB相,以及少量的NbC相;化合物相以细小的块状弥散分布在镍基固溶体中.随着束流和加热时间的增加,接头抗剪强度呈现先升高再降低的趋势.当束流为2.6mA,加热时间为560 s,聚焦电流为1 800 mA时,获得最大抗剪强度为436 MPa的钎焊接头.