Continuous welding of Cu–Ni dissimilar couple using CO 2 laser (original) (raw)
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Continuous welding of Cu–Ni dissimilar couple using CO2laser
Science and Technology of Welding and Joining, 2005
The evolution of microstructure during continuous laser welding of dissimilar metals has been studied for a binary Cu-Ni couple. The effects of laser beam scan speed and laser power on the shape and size of the melt pool, the weldment-substrate interface, the composition profiles, and microstructures of the weldments have been investigated. It is shown that the melt pools exhibit a characteristic asymmetry in shape. The observed microstructure is characterised by the existence of compositional and microstructural variations leading to a banded appearance suggesting localised mixing. Distinct differences exist in the evolution of the microstructure in the copper and nickel sides of the weld pool. An attempt is made to explain some of the experimental observations using thermodynamic and thermal transport arguments.
Characterization of a continuous CO 2 laser-welded Fe-Cu dissimilar couple
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2005
Continuous CO2 laser welding of an Fe-Cu dissimilar couple in a butt-weld geometry at different process conditions is studied. The process conditions are varied to identify and characterize the microstructural features that are independent of the welding mode. The study presents a characterization of the microstructure and mechanical properties of the welds. Detailed microstructural analysis of the weld/base-metal interface shows features that are different on the two sides of the weld. The iron side can grow into the weld with a local change in length scale, whereas the interface on the copper side indicates a barrier to growth. The interface is jagged, and a banded microstructure consisting of iron-rich layers could be observed next to the weld/Cu interface. The observations suggest that solidification initiates inside the melt, where iron and copper are mixed due to convective flow. The transmission electron microscopy (TEM) of the weld region also indicates the occasional presence of droplets of iron and copper. The microstructural observations are rationalized using arguments drawn from a thermodynamic analysis of the Fe-Cu system.
Computational modeling of laser welding of Cu-Ni dissimilar couple
Metallurgical and Materials Transactions B, 2004
A three-dimensional transient model to solve heat transfer, fluid flow, and species conservation during laser welding of dissimilar metals is presented. The model is based on a control volume formulation with an enthalpy-porosity technique to handle phase change and a mixture model to simulate mixing of molten metals. Weld pool development, solidified weld pool shape, and composition profiles are presented for both stationary as well as continuous laser welding in conduction mode. Salient features of a dissimilar Cu-Ni weld are summarized and thermal transport arguments are employed to successfully explain the observations. It is found that the weld pool shape becomes asymmetric even when the heat source is symmetrically applied on the two metals forming the couple. It is also observed that convection plays an important role in the development of weld pool shape and composition profiles. As the weld pool develops, the side melting first (nickel) is found to experience more convection and better mixing. Results from the case studies of computation are compared with corresponding experimental observations, showing good qualitative agreement between the two.
Laser welding of copper–nickel alloys: a numerical and experimental analysis
Science and Technology of Welding and Joining, 2005
Melt run trials were carried out on Cu-Ni bars using a CO 2 laser source in order to analyse the effects of welding parameters (i.e. laser power, welding speed) on geometrical characteristics and on the microstructure of the bead. Experimental results were then used to determine the source parameters to be employed in a finite element model (FEM) of the welding process, with particular attention paid to the thermal field induced by the laser beam. A specific procedure, named 'automatic remeshing technique', was used in order to minimise the computation time. The aim was to create a reliable numerical model, suitable for the optimisation, in practical cases, of welding processes of these kinds of materials. A good correlation, in terms of predicted cooling rates, with the values calculated from SDAS measurements, was observed.
Laser Micro Welding of Dissimilar Material of Aluminum and Copper Alloys
Materials Science Forum, 2017
Copper and aluminum are widely used in electronic industries for their excellence in electric and thermal conductivity. Joining these different material in scale of micro is hardly difficult for their obvious different in thermal properties. Melting these materials during welding process will create intermetallic compound which possesses new material properties. The melted zone became extremely brittle thus increase the possibility of failure due to cracks and concentrated loads. To overcome this problem, fundamental study is needed to characterize the material behavior against heat induction under various processing parameters. This study is an attempt to characterize the performance of Nd-YAG laser in micro joining of Al 1100 and Cu 101.
Microstructural development of dissimilar weldments: case of MIG welding of Cu with Fe filler
Journal of Materials Science, 2002
Microstructure development during MIG welding of copper with iron filler has been studied to gain insight to the process of dissimilar welding. The microstructure of the iron rich bids consist of martensitic bcc iron with cellular network of fcc copper. The scale of network depends on the processing conditions. However, the average composition remains fairly uniform with 20at% Cu excepting at the boundary regions of the bid and the copper plates. A characteristic banded structure could be observed in these regions whose width scales with traverse speed. Evidence of phase separated copper globule suggests access to the submerged miscibility gap and significant undercooling of the melt during welding.
A Review on Melt-Pool Characteristics in Laser Welding of Metals
Advances in Materials Science and Engineering, 2018
Laser welding of metals involves with formation of a melt-pool and subsequent rapid solidification, resulting in alteration of properties and the microstructure of the welded metal. Understanding and predicting relationships between laser welding process parameters, such as laser speed and welding power, and melt-pool characteristics have been the subjects of many studies in literature because this knowledge is critical to controlling and improving laser welding. Recent advances in metal additive manufacturing processes have renewed interest in the melt-pool studies because in many of these processes, part fabrication involves small moving melt-pools. e present work is a critical review of the literature on experimental and modeling studies on laser welding, with the focus being on the influence of process parameters on geometry, thermodynamics, fluid dynamics, microstructure, and porosity characteristics of the melt-pool. ese data may inform future experimental laser welding studies and may be used for verification and validation of results obtained in future melt-pool modeling studies.
Effect of laser welding on mechanical properties of 70/30 Cu-Ni alloy welds
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2014
This article reveals the influence of laser welding process parameter, welding speed, on the mechanical and metallurgical properties of 3.5 kW CO2 laser machine welded joints of 70/30 Cu-Ni alloys. Laser welded joints were fabricated using different welding speeds of 1.0, 1.5, 2.0, and 2.5 m/min. The mechanical properties (hardness, tensile strength, and percentage elongation) of the welded joints were evaluated and correlated with the fusion zone microstructure. Optical microscopy and scanning electron microscopy were used to evaluate the metallurgical characteristics of the welded joints. The joints fabricated using a welding speed of 1.5 m/min exhibited fine, equiaxed, and uniformly distributed grains at fusion zone and resulted in superior mechanical properties than other joints.
CO 2 laser welding of Ni alloy and high temperature steel alloy was carried out on a hollow tubular specimen by varying the laser power and weld speed. Preheating of the specimen and offsetting the laser beam from the centre of the weld joint was adopted as primary strategies to overcome the thermal gradient mismatch which is common in welding of dissimilar materials. The microstructure and hardness were analysed using an optical microscope, a scanning electron microscope (SEM) and a Vickers hardness tester. Welding with laser beam centred at the joint interface caused severe reduction in hardness in the fusion zone. Preheating resulted in cracks in the weld zone. It is observed that laser welding with offset towards Ni specimen had resulted in a weld with full penetration, optimum hardness and without any crack.
Influence of Surface State in Micro-Welding of Copper by Nd:YAG Laser
Applied Sciences
Laser welding of copper is characterized by low and unstable light absorption around 1000 nm wavelength. Combination of high thermal conductivity and low melting point makes it difficult to obtain good welding quality and leads to low energy utilization. To improve efficiency and welding quality, a technique to enhance process stability using 1064 nm wavelength Nd:YAG laser has been proposed, and absorption rate and molten volume in laser micro-welding were discussed. Since the surface state of specimen affects absorption phenomena, effects of surface shape and surface roughness were investigated. Absorption rate and molten volume were increased by creating appropriate concave holes and by controlled surface roughness. Stable micro-welding process with deep penetration and good surface quality was achieved for transitional processing condition between heat conduction and keyhole welding, by enhanced absorption rate.