Mechanical and microstructural investigation of dissimilar joints of Al-Cu and Cu-Al metals using nanosecond laser

Laser beam welding (LBW) has found wide applications in several fields, including electronics, aerospace, and automobile industries, owing to its inherent capabilities over existing welding techniques. Dissimilar laser welding is one of the challenging fabrication processes. However, joining of different materials poses challenging issues because material properties of each material interacts to give rise to hybrid system performance. In present study weld of Al-Cu and Cu-Al has been performed using Ytterbium pulsed fibre laser with a maximum laser power of 300 W. The scanning electron microscope (SEM), and energy dispersive x-ray spectroscopy (EDS) has been employed to investigate the microstructural and chemical composition of the welded joints. The EDS analysis showed the presence of possible intermetallic compounds (IMCs) like AlCu and Cu2Al in the fusion zone. The Al-Cu and Cu-Al welded joints had maximum shear strength of 295 N and 84 N, respectively. The results showed the efficacy of Al-Cu joints over Cu-Al joints. The study further demonstrated that the Al-Cu weld had a better microstructure with fewer pores and cracks than the Cu-Al welds by varying the laser powers.

     

Laser micro-welding of aluminum alloys: experimental studies and numerical modeling

Experimental and numerical studies were conducted on the effects of the laser beam pulse shaping in the time domain on the quality of the welding seam in laser micro-welded AlMg3 with a thickness of 0.2 mm and 1 mm thick AlMg4.5 Mg foils, respectively. The pulse shaping was realized by a time sequence of three different rectangular pulses with different duration and power level. The first pulse was used to pre-heat the sample, welding occurred with the second pulse and the third pulse controlled the melt pool behavior. The power level and the duration of the single pulses were varied systematically and the resulting microstructure was analyzed by scanning electron microscope. The experiments were accompanied by numerical simulations based on a finite volume model which considers the transient heat flow, melt convection and the evolution of a gas capillary during the deep penetration welding process.     

Boundary element analysis of stress singularity in dissimilar metals by friction welding

Friction-welded dissimilar metals are widely applied in automobiles, rolling stocks, machine tools, and various engineering fields. Dissimilar metals have several advantages over homogeneous metals, including high strength, material property, fatigue endurance, impact absorption, high reliability, and vibration reduction. Due to the increased use of these metals, understanding their behavior under stress conditions is necessary, especially the analysis of stress singularity on the interface of friction-welded dissimilar metals. To establish a strength evaluation method and a fracture criterion, it is necessary to analyze stress singularity on the interface of dissimilar metals with welded flashes by friction welding under various loads and temperature conditions. In this paper, a method analyzing stress singularity for the specimens with and without flashes set in friction-welded dissimilar metals is introduced using the boundary element method. The stress singularity index (??) and the stress singularity factor (??) at the interface edge are computed from the stress analysis results. The shape and flash thickness, interface length, residual stress, and load are considered in the computation. Based on these results, the variations of interface length (c) and the ratio of flash thickness (t ₂/t ₁) greatly influence the stress singularity factors at the interface edge of friction-welded dissimilar metals. The stress singularity factors will be a useful fracture parameter that considers stress singularity on the interface of dissimilar metals.     

Ultrasonic welding of dissimilar metals, AA6061 and Ti6Al4V

Ultrasonic welding of Ti6Al4V sheet and A6061 aluminum alloy sheet was conducted. The influence of ultrasonic welding parameters on the mechanical properties, the interface microstructure, the micro-hardness and the composition diffusion of the welded joint was investigated. It was shown to be possible to join Ti6Al4V sheet and A6061 aluminum alloy sheet through ultrasonic welding. After ultrasonic welding, the hardness of both the matrices increased, and there appeared to be some amount of diffusion across the welding interface. Various welding pressures and welding times were used and the strength of the welded joint was at its optimal value with a welding pressure of 0.4?MPa and a welding time of 170?ms.     

Cu—Al合金体系中微观组织结构的优化控制

以典型的共析体系合金Cu-Al合金为研究对象,对其进行了恰当的热处理和等径角变形(ECAP)处理,研究了该合金中先共析相与共析相的组织变化规律.研究结果表明:Cu-Al中的先共析相尺寸在热处理过程中随着冷却速度的增加而变得细小,组织分布更加弥散,并且在随后的等径角变形中将发生剪切变形,而在退火过程中又会长大;Cu-Al中的共析相则在热处理过程中因冷却速度的不同而转变成不同的组织,其中转变成的β马氏体在等径角变形中开始发生分解,并在随后的退火过程中进一步完全分解成α+γ2混合组织.     

Effect of dissimilar metals on fretting fatigue behavior of Ti–6Al–4V

An investigation was conducted to explore fretting fatigue behavior of Ti–6Al–4V specimens in contact with pads of varying composition. Four conditions were selected to provide a range of compositions: Ti–6Al–4V (with two surface finishes), aluminum and nickel. Behavior against each pad condition was evaluated for two pad geometries (cylinder-on-flat, blended flat-on-flat) in two separate test fixtures. Experiments were conducted with varying applied fatigue stresses and contact forces. Applied clamping stresses for the flat-on-flat pads were 200 and 650 MPa. For the cylinder-on-flat geometry, forces were selected to provide Hertzian peak pressures of 292 and 441 MPa. The coefficient of friction, μ, was quantified and pad surfaces were characterized through hardness and composition evaluation. Finite element analyses of the test fixtures were conducted to assess variations in the stress fields.     

基于功能分析的铜-铝管对焊机的设计

为实现铜-铝管的优质焊接,需要研制相应的焊接设备。以系统的观点采用功能分析法进行分析设计,通过对总功能的分解和原理解的组合,得到了铜-铝管对焊机的形态学矩阵。通过对形态学矩阵中各方案的分析评价,得到了最佳的可行方案。实践证明,用这种设计方法研制出的铜-铝管对焊机,为企业带来良好经济效益。     

Cu-Al2O3复合材料的塑性变形分析

用Gleeble-1500型热模拟机对Cu-Al2O3复合材料的塑性变形进行了试验分析。结果表明，在300～600℃，ε≤1／s时，随着应变的增加，复合材料的流动应力迅速达到极值点后，逐步减小；变形时温度变化较小，并且变形后晶粒无粗化现象；还分析了温度及应变速率的影响。     

铜铝复合板渐进成形回弹缺陷研究

为了讨论不同工艺参数对复合板渐进成形回弹的影响,建立了包含工具头、复合板材和复合界面的三维有限元模型,通过对比T形剥离结果得到复合界面内聚力单元参数,通过实验验证了有限元模型的可靠性.实验结果表明,成形角对双金属复合板渐进成形回弹最敏感,工具头直径对回弹敏感度最低,另外,内聚力单元能有效模拟双金属复合板结合界面,模拟误...     

Laser acoustic method for the inspection of flaws in metals and the metallized coatings of dielectrics

The propagation of acoustic waves in an aluminum specimen without flaws and in specimens with artificial flaws is considered. A method for the combined diagnostics of metal surfaces of materials using the developed experimental system was suggested on the basis of the performed analysis of the time travel and reflection diagrams of ultrasonic waves.     

Cyclic tangential loading of dissimilar elastic bodies

A two-dimensional fretting fatigue problem involving normal and tangential loading of dissimilar elastic bodies in contact is analyzed. The bodies are brought into contact by a monotonic normal load and then a cyclic tangential load is superimposed with the normal load held constant. The Hertz half plane assumption is retained for each body and the region of contact is divided into a central zone of stick and two external regions of micro-slip in each of which the Amontons-Coulomb law of sliding friction is assumed to apply. The effect of the interaction between the normal and shear stresses due to the mismatch in elastic constants is quantified by comparing the present rigid-elastic numerical solution (extreme case) to the Cattaneo-Mindlin closed form solution for elastically identical materials.     

Review on electromagnetic welding of dissimilar materials

Electromagnetic welding (EMW) is a high-speed joining technique that is used to join similar or dissimilar metals, as well as metals to non-metals. This technique uses electromagnetic force to mainly join conductive materials. Unlike conventional joining processes, the weld interface does not melt, thus keeping the material properties intact. Extremely high velocity and strain rate involved in the process facilitate extending the EMW technique for joining several materials. In this paper, the research and progress in electromagnetic welding are reviewed from various perspectives to provide a basis for further research.     

Decomposition of interfacial crack driving forces in dissimilar joints

This paper presents a framework how to estimate crack driving forces in terms of crack-tip opening displacement andJ-integral for mismatched dissimilar joints with interface cracks. The mismatch in elastic, thermal, and plastic hardening properties is not considered, but the mismatch in plastic yield strengths is emphasized here. The main outcome of the present work is that the existing methods to estimate crack driving forces for homogeneous materials can be used with slight modification. Such modification includes (i) mismatch- corrected limit load solutions, and (ii) evaluating the contribution of each material in dissimilar joints to the total crack driving force, which depends on the strength mismatch of the dissimilar joints.     

Subsurface nanoindentation deformation of Cu-Al multilayers mapped in 3D by focused ion beam microscopy

A new technique for the three-dimensional analysis of subsurface damage of nanocomposites is presented. Cu–Al multilayers, grown epitaxially on (0001)Al₂O₃ single crystals by ultra high vacuum molecular beam epitaxy, have been deformed by nanoindentation. Systematic slicing and imaging of the deformed region by focused ion beam microscopy enables a 3D data set of the damaged region to be collected. From this 3D data set, profiles of the deformed sub-surface interfaces can be extracted. This enables the deformation of the individual layers, substrate and overall film thickness to be determined around the damage site. These 3D deformation maps have exciting implications for the analysis of mechanical deformation of nanocomposites on a sub-micrometre scale.     

Studies of high temperature sliding wear of metallic dissimilar interfaces

The evolution of microstructures in the glaze layer formed during limited debris retention sliding wear of Nimonic 80A against Stellite 6 at 750 °C and a sliding speed of 0.314 m s⁻¹ (7 N applied load, 4522 m sliding distance) was investigated using scanning electron microscopy (SEM), energy dispersive analysis by X-ray (EDX), X-ray diffraction (XRD), scanning tunnelling microscopy (STM) and transmission electron microscopy (TEM). The collected data indicate the development of a wear resistant nano-structured glaze layer. The process of ‘fragmentation’ involving deformation, generation of dislocations, formation of sub-grains and their increasing refinement causing increasing misorientation was responsible for the formation of nano-structured grains. The rapid formation of this glaze layer from primarily cobalt–chromium debris transferred from (and also back to) the surface of the Stellite 6, kept wear of both the Nimonic 80A and Stellite 6 to very low levels.However, increasing the sliding speed to 0.905 m s⁻¹ (750 °C) suppressed glaze formation with only a patchy, unstable glaze forming on the Stellite 6 counterface and an absence of glaze development on the Nimonic 80A sample (the Nimonic 80A surface was covered with at most, a very thinly smeared layer of oxide). The high levels of oxide debris generated at 0.905 m s⁻¹ instead acted as a loose abrasive assisting wear of especially the Nimonic 80A. This behaviour was attributed to a change in oxide chemistry (due to the dominance of nickel and chromium oxides generated from the Nimonic 80A) resulting in poor oxide sintering characteristics, in combination with increased mobility and reduced residency of the oxide debris at 0.905 m s⁻¹.     

Three-dimensional numerical modeling of the friction stir welding of dissimilar steels

It is now widely recognized that collaboration across the supply chain is a must to be improved to achieve competitive advantage in global markets. Despite the fact that there is a unique well-known concept for supply chain collaboration suggested by the Voluntary Interindustry Commerce and Standards Committee (VICS), it is far from being enough as a solo source for a successful implementation because of being industry-dependent (particular for retail industry), abstract, qualitative, and inflexible. This research fills the gaps in VICS’s method by addressing a holistic and structured Collaborative Planning, Forecasting and Replenishment (CPFR) roadmap, which provides a complete source for practitioners and academicians for effective supply chain collaboration to be implemented widespread across any industry. A real case study was also carried out between an automotive supplier company and its aftermarket customer to demonstrate the benefits of the proposed CPFR roadmap in terms of specified key performance indicators as well as a discussion about how the suggested roadmap behaved in the practice.