| Due to the low density, excellent processing performance, corrosion resistance and good plasticity, aluminum alloy has been widely used in industry in various fields. And as the aluminum alloy with highest strength in general temperature, 7075 aluminum alloy gradually becomes important material selection in the aerospace, automotive and other industries. Using the general method of welding is hard to get a better quality of welds and joints for 7075 aluminum alloy. Laser which can concentrate high energy in small area make the local temperature of work piece rise quickly to meet or exceed the melting point. Laser welding which is a relatively ideal welding choice is characterized by rapid welding speed, little deformation, beautiful welding seam and small heat affected zone.The welding seam shape and welded joint of laser welding for 1 mm 7075 aluminum alloy plate is studied in this paper. And the effects on welding seam formation and molten pool shape from welding current, pulse width and frequency are studied. The microstructure and micro hardness of welding joint is also analyzed. The results show that the laser welding seam is smooth and beautiful, and the process parameters of welding have obvious effects on weld width and weld penetration. The welding current makes the seam end sag when undersize while form pores when excessive. Pulse width is proportional to the welding width and welding penetration which the laser frequency is inversely proportional to. That is because the increase of pulse width increases welding heat input time, and higher frequency decrease the energy density of single frequency. The grains of weld microstructure are smaller than of parent metal organization and the micro hardness of parent metal area, welding zone, melting area shows a trend of decline in turn.The temperature field of aluminum alloy laser welding is simulated by the selection of the combined heat source with Gauss heat source and cone plane heat source based on the finite element software ANSYS. By compiling APDL language program to achieve the load of moving heat source, the characteristic of material parameters variation with temperature is considered, the welding temperature distribution and temperature time-varying characteristics are analyzed, and the single factor influence on the temperature field from process parameters and heat source model parameters is studied. The difference from using a single plane gauss heat source model to the combined heat source model is also comparatively analyzed and the example of full penetration laser welding is introduced. Results show that the welding seam area of the high temperature areas focus near the weld zone with the input of laser energy and temperature of laser zone under the action of laser approximately rises by step shape. The advantage of combined heat source model in the study of low power laser welding is not obvious. Then the numerical simulation can achieve high coincidence with the experiment, which illustrates the rationality and accuracy of the simulation.The research on welding test and process parameters of 7075 aluminum alloy in this paper provides the reference to the optimization of high strength aluminum alloy welding process and the numerical simulation of temperature field lays a solid foundation on stress analysis for aluminum alloy welding and the choice of welding parameters. |
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