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Effects of titanium on grain boundary strength in molybdenum laser weld bead and formation and strengthening mechanisms of brazing layer
摘要： Molybdenum has tremendous application potential in the nuclear power field, but its application is limited by the grain-boundary embrittlement of fusion-welded joints made of it. In this study, titanium was selected as an alloying element to reduce brittleness of laser weld beads in molybdenum "cladding-end plug" socket joints. Brazing was also performed to enhance the joint strength. Joints with the same strength as base material and a hydraulic bursting pressure of 60 MPa were produced using a combination of the two methods. The analysis indicates the following. After being added to the weld bead, titanium was able to combine with the free oxygen, forming TiO2 and reducing the MoO2 content on grain boundary surface. Oxygen and MoO2 are both the main causes of the embrittlement of molybdenum grain boundaries. In addition, by taking advantage of the high melting point and thermal conductivity of molybdenum, a titanium foil pre-placed between the tube and rod in the socket joint was melted, forming metallurgical bonding, which further improved the bearing capacity of the joint.
关键词： laser beam welding,titanium,brazing,molybdenum,grain boundary embrittlement
更新于2025-11-28 14:24:20
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Butt welding-brazing of steel to aluminum by hybrid laser-CMT
摘要： A laser penetration welding-brazing combined with Cold Metal Transfer (CMT) arc, was proposed to improve weld shape and interfacial reaction inhomogeneity of 5052 aluminum alloy and Q235 low carbon steel with ER5356 welding wire in butt joint. The effects of wire feed speed, beam offset and welding speed on weld shape, interfacial microstructures and tensile strength of joints was studied. This method improved the undercut defect existed in butt laser welding-brazing, obtained well-formed joints and promoted the uniform distribution of the interface reaction. The interfacial intermetallic compounds (IMCs) layer consisted of Fe2Al5 and Fe4Al13 and the thicknesses were controlled to 3-5 μm. Microstructures of weld seam was composed of α-Al and Al3Mg2. The brittle IMCs layer thickened and then the tensile strength decreased with increasing the wire feed speed. The thickness of the IMCs layer decreased but weld shape became worse when the welding speed or the offset increased. The tensile strength increased first and then decreased. The highest tensile strength reached higher than 80 MPa and the joint fractured in IMCs layer along the interface.
关键词： intermetallic compound,Laser–CMT arc hybrid welding-brazing,dissimilar metals welding,low carbon steel,aluminum alloy
更新于2025-11-28 14:24:20
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Interface characterization and mechanical properties of dual beam laser welding-brazing Al/steel dissimilar metals
摘要： The DP590 steel to AA7075 Al-alloy with lap configuration is successfully joined by dual beam laser welding-brazing without using filler metal. Through the introduction of the derived laser beam, the wetting angle, wetting distance and the thickness of intermetallic compound (IMC) layer are well improved and controlled. It is found that the wettability of liquid Al on steel improves with the increase of laser power, i.e. the wetting angle decreasing from 25.3° to 17.8° and the wetting distance increasing from 2.17 mm to 3.19 mm as the laser power increasing from 1.0 kW to 1.6 kW. Two kinds of IMC exist at brazing interface, one is η-phase (Fe2Al5) with flatten morphology closing to the steel side and the other is θ-phase (FeAl3) with needle-like morphology adjacent to the welding-brazing seam. The thickness of IMC layer increases from 8.37 μm to 12.12 μm with increasing laser power from 1.0 kW to 1.6 kW. Tensile test shows that both the wettability and the IMC thickness have influence on the welding-brazing joint strength. Poor wettability and too thick IMC layer will result in lower strength and fracture occurred in brazing interface. The optimal joint tensile strength of 123.7 MPa on average is achieved with the laser power of 1.4 kW.
关键词： Tensile strength,Welding-brazing,IMC,Dual beam laser,Al/steel dissimilar metals
更新于2025-11-28 14:24:20
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Microstructure and mechanical properties of Ti/Al dissimilar joints produced by laser-MIG welding–brazing
摘要： We butt-welded AA6061 aluminum alloy to Ti6Al4V titanium alloy, dissimilar light metals, by using laser-MIG hybrid welding–brazing without grooves. The parameters of the laser and arc were optimized to produce sound joints with good formation and mechanical properties. The microstructure of the layer of intermetallic compounds (IMCs) was investigated by scanning electron microscopy and energy dispersive spectroscopy. We also tested the tensile strength of the joints with and without reinforcement. The morphology and thickness of the IMCs varied throughout the joints. A continuous thin layer of TiAl3 appeared on the top surface of the Ti6Al4V, on which some rod-like IMCs grew toward the fusion zone. In the upper region of the butt plane, because more heat accumulated there from the high-power laser coupled with the MIG arc, double-layer IMCs with a thickness of ～ 10.0 μm formed, composed of TiAl (near the Ti alloy) and TiAl3 (near the fusion zone). In the lower region of the butt plane, the double-layer IMCs became continuous and uniform, the serrated morphology disappeared, and the thickness of the IMC layer decreased to 4.0 μm. On the backside of the joint, the thickness of the compound layer (TiAl3) was about 1.0 μm. The average tensile strengths of the reinforced and unreinforced joints were 226 MPa and 210 MPa, respectively, which are up to 88% and 81% of the AA6061 tensile strength, respectively.
关键词： dissimilar joint,titanium alloy,intermetallic compounds.,Laser-MIG hybrid welding–brazing,aluminum alloy
更新于2025-09-23 15:22:29
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Stability of carbon nanotube cold cathode electron beam (C-beam) with vacuum brazing process
摘要： A modularization of electronic parts in electrical devices is a key feature for system integration. Especially, x-ray tube fabrication process has been stayed in an obsolete manner due to the utilizing of classical thermionic x-ray sources. But cold cathode emitters such as carbon based materials with nanoscale dimension are expected to replace the conventional wired tungsten filaments due to their outstanding electrical and mechanical properties. To facilitate cold cathode emitter as an x-ray source, state of the arts bonding techniques are required. In this study, carbon nanotube grown Si wafers were successfully bonded to the metal carrier via vacuum brazing process and no electrical degradation of CNT (carbon nanotubes) emitters were observed after the process. Finally, we evaluated the stability of electron beam current density for device reliability. We expect that the cost-effective and facile technique could be applied for cold cathode based x-ray tube manufacturing process.
关键词： carbon nanotubes (CNTs),brazing,x-ray tube,junction,cold cathode
更新于2025-09-23 15:21:21
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Influence of the Wire Feeding on the Wetting Process during Laser Brazing of Aluminum Alloys with Aluminum-Based Braze Material
摘要： The wetting behavior in laser brazing can be designated as inconstant, caused largely by external process discontinuities such as the wire feeding. To reveal periodic melt pool propagation effects that occur during laser brazing of aluminum and for a better understanding of those effects in laser brazing in general, this paper analyzes high-speed recordings of the brazing process with aluminum alloy. It is demonstrated that two main effects of periodic melt pool behavior in different frequency scales occur during the process, related directly to the wire feeding.
关键词： laser brazing,aluminum,process frequencies,melt pool behavior,process dynamics
更新于2025-09-23 15:21:01
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Investigations on the occurrence of different wetting regimes in laser brazing of zinc-coated steel sheets
摘要： In the automotive industry, the seam edge quality of laser brazed seams is a crucial factor for the required high optical quality standards of customer-visible connections of zinc-coated car body parts. The type of zinc coating is decisive for the resulting geometry of the seam edges, which are aspired to be straight. Especially brazing of hot-dip galvanised steel with conventional brazing setup is not resulting in seam edges which fulfil the required optical quality. In this study, the wetting of copper-based filler wire on electrogalvanised and hot-dip galvanised steel sheets is analysed to increase the understanding of the influence of the wetting fronts on the seam edge quality. For this, the wetting fronts are determined in high-speed camera images and the resulting seam edges are captured by microscopic pictures. The results show that two major wetting regimes occur on both types of zinc coatings but with a different occurrence probability: one with a steep wetting front and zinc evaporation in front of wetting (“steep-angle-wetting”) and one where liquid zinc connects with the wetting front and creates a flat wetting angle (“flat-angle-wetting”). It is found that the resulting seam edge quality is mainly depending on the present wetting regime. However, for flat-angle-wetting, in the regime with insufficient seam edge quality, a self-stabilising effect is identified, which is responsible for a missing process window for brazing of hot-dip galvanised steel with sufficient seam edge quality.
关键词： Wetting,Optical seam quality,Laser brazing,Zinc-coated steel
更新于2025-09-23 15:21:01
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Microstructure and mechanical properties of welding–brazing of Ti/Al butt joints with laser melting deposition layer additive
摘要： Laser welding–brazing of Ti/Al butt joints was performed with coaxial Al–10Si–Mg powders feeding. The experimental results indicated that a sound Ti/Al butt joint could be obtained by an additive layer approach. The influence of the laser melting deposition layers on the weld appearance, interfacial microstructure and tensile properties were investigated. High-quality joints were produced when five and seven layers were deposited. The morphology and thickness distributions of the interfacial intermetallic compounds (IMC) at the brazing interface along the thickness direction of the joint varied with the number of deposition layers. Continuous serrated IMC was obtained in joints produced by seven deposition layers, and the IMC layer was distributed homogenously along the thickness direction. The maximum thickness difference of the IMC was only approximately 0.12 μm. The microstructure of the IMC layer was composed of a nanosized granular Ti7Al5Si12 phase and serrated Ti(Al, Si)3 phase. The maximum tensile joint strength reached 240 MPa, 80% of that of the aluminum base metal, and the lower tensile strength of the other joints was caused by insufficient IMC layer or a porosity defect.
关键词： Tensile strength,Laser melting deposition,Interfacial IMC,Laser welding–brazing,Ti/Al butt joint
更新于2025-09-19 17:15:36
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Wettability, microstructure and properties of 6061 aluminum alloy/304 stainless steel butt joint achieved by laser-metal inert-gas hybrid welding-brazing
摘要： Laser?metal inert-gas (MIG) hybrid welding?brazing was applied to the butt joint of 6061-T6 aluminum alloy and 304 stainless steel. The microstructure and mechanical properties of the joint were studied. An excellent joint-section shape was achieved from good wettability on both sides of the stainless steel. Scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffractometry indicated an intermetallic compound (IMC) layer at the 6061-T6/304 interface. The IMC thickness was controlled to be ~2 μm, which was attributed to the advantage of the laser?MIG hybrid method. Fe3Al dominated in the IMC layer at the interface between the stainless steel and the back reinforcement. The IMC layer in the remaining regions consisted mainly of Fe4Al13. A thinner IMC layer and better wettability on both sides of the stainless steel were obtained, because of the optimized energy distribution from a combination of a laser beam with a MIG arc. The average tensile strength of the joint with reinforcement using laser?MIG hybrid process was improved to be 174 MPa (60% of the 6061-T6 tensile strength), which was significantly higher than that of the joint by traditional MIG process.
关键词： laser?metal inert-gas hybrid welding,microstructure,butt joint,welding?brazing
更新于2025-09-19 17:13:59
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Numerical Simulation and Parameters Optimization of Laser Brazing of Galvanized Steel
摘要： In order to study the heat phenomenon of laser brazing galvanized steel, the experiments of laser brazing were carried out, in which the base metal is galvanized steel sheets and CuSi3 is used as filler metal. The numerical simulation of temperature field was carried on by the finite element method, and the simulation result was validated through comparative experiment. The composite heat source model of gauss double ellipsoid was used. Temperature field of different process parameters have been calculated. The results show that: The peak temperature and temperature gradient on the joint are lower when the laser power is 1 600 W, the brazing speed is 0.96 m/min. Response surface methodology was applied to the simulation data, and mathematical models was built based on Box-Behnken Design using linear and quadratic polynomial equations. The results indicate that the proposed models predict the responses adequately within the limits of brazing parameters being used. The optimum brazing parameters were found, and it is more favorable to form the brazed joint of good quality at the laser power of 1 600 W, brazing speed of 0.96 m/min, filler wire speed of 1.19 m/min, defocusing distance of 30 mm.
关键词： numerical simulation,laser brazing,response surface methodology,optimization
更新于2025-09-19 17:13:59