Research On Selective Laser Melting Forming Quality And Process Optimization Of Aluminum Alloy Overhang Circular Hole

Aluminum and its alloys are the main materials for any structure except steel and iron,which are suitable for various industrial fields.Selective Laser Melting(SLM)technology can optimize the structure of complex metal parts and carry out new designs to ensure performance.However,problems such as suspension surface collapse and high suspension surface roughness exist in the SLM processing of aluminum alloy suspension structures.To improve the SLM forming quality of the aluminum alloy overhanging structure,the aluminum alloy overhanging circular hole structure is taken as the research object.The influence of laser process parameters on the forming quality is explored by combining simulation and experiment.The forming process is optimized to improve the forming quality.The main research contents and conclusions are as follows:(1)The structure model of overhanging circular hole is designed.With the help of simulation tools,the SLM process of overhanging a circular hole is simulated.According to the stress and displacement cloud diagram,the size change of forming a circular hole is analyzed.The results show that the whole model has a certain degree of deformation.The displacement of the peripheral size mainly occurs at the corner of the model.The displacement of the internal hole size is mainly concentrated in the overhanging area,and the displacement of the non-overhanging area is small.(2)A single-factor experiment is designed to investigate the influence of laser process parameters on the dimensional accuracy of overhanging circular holes.The results show that the laser power,scanning speed,and scanning spacing mainly control the flow behavior and solidification morphology of the molten pool by changing the energy of the laser transmitted to the powder,thus affecting the dimensional accuracy of the round hole.The laser scanning line angle mainly affects the size accuracy of the round hole by affecting the contact between the molten pool and the powder.(3)The influence of laser process parameters on the forming quality of overhanging round holes is investigated with density and hardness as indexes.The results show that with the increase of laser power,the density and hardness of the formed parts increase first and then decrease.The influence of scanning speed and scanning distance on each performance has the same rule.(4)The concept of laser energy density is introduced to comprehensively consider the influence of various laser factors on the quality of formed aluminum alloy overhanging circular holes.Based on the results of laser single-factor research,the forming optimization scheme is proposed: the laser power of 300 W,scanning speed of900 mm/s,scanning interval of 0.15 mm,and Inclined partition of 67 ° are used to form the non-overhanging part of the circular hole.The laser power is 200 W,the scanning speed is 900 mm/s,and the scanning interval is 0.14 mm to form the overhanging part of the circular hole.And the scanning line angles of 0 ° and 90 ° are used to form the overhanging areas II and III respectively;When the formed overhanging part meets the support conditions,the laser parameters are continuously adjusted to form the non-overhanging part of the circular hole.The experimental verification of the optimized scheme shows that the circular hole has high dimensional accuracy.And the solid part has good mechanical properties.