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Characterization of electron beam welded AA2024   总被引:2,自引:0,他引:2  
P. Wanjara  M. Brochu 《Vacuum》2010,85(2):268-282
For aerospace manufacturing, the perseverance for improving performance (high strength to density ratio) and reducing weight and costs has motivated consideration of welding techniques applicable to aluminum alloys. During fusion welding of aluminum alloy (AA) 2024, the avoidance of defects (e.g., porosity, oxides, solidification cracking, undercutting) and the optimization of the microstructure-property characteristics are of critical concern. In this work, AA2024 was electron beam (EB) welded as part of a study to determine the influence of parametric conditions on the characteristics of the weldment to optimize the joining process. Specifically, the evolution in the weld geometry, microstructure and mechanical properties was examined as a function of the process conditions, including beam current, beam focus, beam oscillation, and welding speed. For optimized parametric conditions, microstructural examination of the joints revealed narrow fusion and heat-affected zones comprising of dendritic structures without the occurrence of defects that enabled a maximized joint efficiency.  相似文献
2.
The optimum processing conditions for joining thin sheet materials (1-3.2 mm) of commercial purity titanium and Ti-6%Al-4%V by electron beam welding were determined by using single- and double-pass melting sequences. For commercial purity titanium weldments, the tensile properties were observed to be similar to the parent material and independent of the sheet thickness and the welding procedure. However, for Ti-6%Al-4%V, the processing conditions during welding were observed to change the characteristics of the alpha lamellae spacing and plate thickness, which in turn influenced the properties. Hence, for joining alpha-beta titanium alloys with use of electron beam welding, the definition of critical processing conditions enables optimization of the structure-property characteristics of the joint.  相似文献
3.
In hypereutectoid steels, determination of interlamellar spacing is essential to microstructural characterization, since both static and dynamic properties have been related to the pearlitic structure. Generally, quantitative analysis of the size of a pearlite colony and its interlamellar spacing is performed using optical and electron microscopy techniques. In this work, laser scanning confocal and field emission scanning electron microscopes were used to examine interlamellar spacing in isothermally transformed hypereutectoid steels to benefit from increased resolving power and statistical significance capabilities as compared to light optical and transmission electron microscopes, respectively.  相似文献
4.
Ti–5Al–5V–5Mo–3Cr (Ti-5553) sheets were welded using a Nd: YAG laser system and Ti–6Al–4V filler wire. The effect of joint gap on weld geometry, defects, microstructure, and hardness was investigated. Fully penetrated welds up to a joint gap of 0.5 mm were produced. The two main defects observed were porosity and underfill. The addition of filler wire reduced underfill but increased porosity, especially at large joint gaps. The fusion zone (FZ) microstructure at low joint gaps consisted of retained β with a dendritic morphology. At a joint gap of 0.3 mm, regions of orthorhombic α″ martensite were observed in the weld zone which increased in proportion as the joint gap increased from a volume percentage of 4.9% at 0.3 mm to a volume percentage of 44% at 0.5 mm. Despite the differences in microstructure with increasing joint gap, the FZ hardness remained relatively constant for all joint gaps evaluated.  相似文献
5.
Hybrid laser – metal active gas (MAG) arc welding is an emerging joining technology that is very promising for shipbuilding applications. This technique combines the synergistic qualities of the laser and MAG arc welding techniques, which permits a high energy density process with fit-up gap tolerance. As the heat input of hybrid laser – arc welding (HLAW) is greater than in laser welding, but much smaller than in MAG arc welding, a relatively narrow weld and restricted heat affected zone (HAZ) is obtained, which can minimize the residual stress and distortion. Furthermore, adding MAG arc can increase the penetration depth for a given laser power, which can translate to faster welding speeds or fewer number of passes necessary for one-sided welding of thick plates. In this work, a new hybrid fiber laser – arc welding system was successfully applied to fully penetrate 9.3 mm thick butt joints using a single-pass process through optimization of the groove shape, size and processing parameters.  相似文献
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