Numerical Simulation And Experiment Study On Selective Laser Melting Of Metal Powders

Selective Laser Melting (SLM) technology which is based on Selective Laser Sintering (SLS) can produce strong metallic models directly from metal powders; metallic of single composite are successively melted in a microscopic zone by laser energy and solidify without leaving much porosity. The part can be made it possible to produce nearly 100% dense metal from customary metal powder. However, time between material melt and solidification is so short that temperature gradient is very large, which easily lead to bring forth many defect such as remain stress and cracks. In order to obtain appropriate processing parameters, revealing mechanisms of SLM process is the imperative work.In the study of SLM process mechanisms, both computer numerical simulation and experiment method are employed. Finite element model of SLM process is modeled by ANSYS Parametric Design Language (APDL), initial conditions and boundary conditions are set according to experiment environment, and then temperature distribution is calculated. The result can predict melted pool dimension and also shows the relation between temperature distribution, molten pool dimension and process parameters. The experiment process parameters can be selected appropriately according to numerical analysis result.In SLM process, remain stress would be caused by material expansion and contraction in very short time, temperature gradient play an important role in this process. Coupled-field of thermal-structure analysis is carried out when thermal analysis is finished, and stress distribution which is caused by temperature gradient is visualized showed. In order to reduce and improve remain stress distribution, the method of preheating powders and changing sweep strategy are brought forward in experiment.The optimization process parameters are determined according to numerical simulation result. The experiment platform is HRPM equipment which is developed in our laboratory, in the process, experiment parameters and simulation parameters are the same. The experiment result show that optimization parameters obtain from simulation result can produce part without many defects. Meanwhile, lattice structure part is easily formed because of its special structure.At the end of thesis, the summary of thesis is made, and some suggestions to improve SLM part performance are prospective proposed.