Laser Micromotion Scanning Composite Arc Additive Manufacturing Molten Pool Melt Solidification Structure Control Process Research

Additive manufacturing technology has the process characteristics of point-bypoint melting and layered manufacturing,which can realize the rapid manufacturing of3 D complex structural parts and high performance of materials.In this paper,we propose a research on the regulation of the melt solidification structure of the arc additive manufacturing melting pool based on laser micromotion scanning,and analyze the experimental process and the regulation mechanism respectively.The effects of laser scanning mode,laser power,laser amplitude,laser scanning speed,laser energy output mode and other main process parameters on the macroscopic morphology and microstructure of forming structure were analyzed.A finite element analysis model based on the 3D heat source was established,and numerical simulations were performed to analyze the mechanism of laser micromotion scanning to improve the microstructure by changing the temperature and flow fields of the melt pool in terms of temperature and flow fields,respectively.The results show that the linear scanning of the laser beam can stabilize the arc deposition process and improve the edge flatness of forming structure;the optimized process parameters can obtain the deposited layer structure with the smallest sidewall roughness and machining allowance;in the macroscopic forming,increasing the laser energy will reduce the deposited layer height,increasing the laser scanning amplitude will increase the deposited layer width,and increasing the laser scanning speed will reduce the deposited layer height.The scanning behavior of the laser beam can increase the oscillation effect of the melt pool,effectively blocking the growth of columnar crystal dendrites and reducing the grain size.Moreover,the grain size decreases gradually with the increase of laser scanning speed,and the optimal orientation of grain growth is improved when the scanning speed is above than 1200 mm/s.Under the condition of changing the laser energy output,the pulsed laser linear scanning process with a pulse frequency of 50 k Hz can further optimize the grain morphology based on the continuous laser linear scanning.It was found that both continuous laser linear scanning and pulsed laser linear scanning could produce fine grain strengthening effect,and the tensile strength and elongation in both transverse and longitudinal directions were improved,and the pulsed laser linear scanning had the best overall mechanical properties.