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Chen H.,Northwestern Polytechnical University | Chen H.,Shaanxi Key Laboratory of Friction Welding Technologies | Peng J.,Shaanxi Key Laboratory of Friction Welding Technologies | Fu L.,Northwestern Polytechnical University | And 3 more authors.
Applied Surface Science | Year: 2016

In order to reduce or even replace the use of Sn-Pb solder in electronics industry, the laser-textured surface microstructures were used to enhance the wetting behavior of lead free solder during soldering. According to wetting theory and Sn-Ag-Cu lead free solder performance, we calculated and designed four microcosmic structures with the similar shape and different sizes to control the wetting behavior of lead free solder. The micro-structured surfaces with different dimensions were processed on copper plates by fiber femtosecond laser, and the effect of microstructures on wetting behavior was verified experimentally. The results showed that the wetting angle of Sn-Ag-Cu solder on the copper plate with microstructures decreased effectively compared with that on the smooth copper plate. The wetting angles had a sound fit with the theoretical values calculated by wetting model. The novel method provided a feasible route for adjusting the wetting behavior of solders and optimizing solders system. © 2016 Elsevier B.V. All rights reserved. Source


Chen H.-Y.,Northwestern Polytechnical University | Chen H.-Y.,Shaanxi Key Laboratory of Friction Welding Technologies | Fu L.,Northwestern Polytechnical University | Fu L.,Shaanxi Key Laboratory of Friction Welding Technologies | And 2 more authors.
Acta Metallurgica Sinica (English Letters) | Year: 2015

Ti-6Al-4V rods were butt-welded by rotary friction welding in this study. Additionally, the radial differences in microstructure and mechanical property of joints were investigated by hierarchy slicing method. The results displayed that the width of weld zone and heat-affected zone of joints became wider along radial direction. Meanwhile, the tensile strength of joints decreased gradually along the radial direction. According to the theoretical analysis, the temperature gradient and inhomogeneous forging pressure leaded to the radial differences. Through K-type thermocouples, the actual temperatures at different locations were measured, and the results were consistent with the theoretical analysis. Theoretically, the radial differences of rotary friction welding joint are an inherent phenomenon; thus, the size of weldment should be limited strictly below the corresponding critical size. In order to prevent radial differences from enlarging, the welding surface profile of weldment can be processed into oval shape, and a larger forging pressure can be used within the scope of the joint deformation allowed according to causes for radial differences. © The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg 2015. Source

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