Research On SLM Forming Quality Evaluation And Process Optimization Of Titanium Alloy Parts With Internal Channels

Titanium alloy is widely used in aerospace,automobile and energy industries due to their high temperature resistance,low density,high specific strength.However,due to their active chemical properties,titanium alloy is easy to occur oxidation at high temperature.During the cutting process,sticking phenomenon occurs easily too,which seriously affects the forming accuracy.In addition,it is difficult to process some parts with complex internal structure by traditional processing method,especially after the processing is completed,the internal structure can not be further processed.Selective Laser Melting(SLM),as a widely used method of additive manufacturing,with the characteristics of forming any complex structure,simple processing technology and short design cycle.Therefore,based on the theory of selective laser melting,this paper focus on the influence of scanning strategy on the forming precision,the influence of process parameters on the forming precision of titanium alloy with internal channels and the optimization of selective laser melting processing parameters.The main research contents are as follows:1.Study on laser and powder interaction mechanism and molten pool theory.The energy transfer form of laser between powders,the absorption and conversion of laser energy by metal materials and the heating mechanism of laser powder on metal powder materials are introduced.The influence of convection on the forming morphology of molten pool is analyzed based on the melting and solidification mechanism of metal powder.The influence of laser power,scanning speed,scanning spacing and scanning strategy on SLM forming temperature field is analyzed by ANSYS simulation.2.Research on the influence of scanning strategy on forming accuracy.The raw material powder of Ti-6Al-4V titanium alloy was treated by physical method.The influence of powder fluidity on forming accuracy was studied and the optimal powder was determined.Then the influence of three scanning strategies on surface roughness,dimensional accuracy and position error of forming parts was studied.The optimal scanning strategy is the spiral scanning strategy,which provides the basis for the subsequent study.3.Research on the influence of process parameters on the forming precision of titanium alloy parts with inner channels.The effects of laser power,scanning speed and scanning space on the forming accuracy of different sizes of titanium alloy parts with inner channels were studied.The variation of dimensional error,flatness and roughness and the suitable process parameters were obtained.Based on the obtained process parameters,the single factor experiment method was used to study the effects of laser power,scanning speed and scanning space on the dimensional accuracy,flatness and roughness of 3mm inner channel,the influence of process parameters on the forming accuracy of titanium alloy parts with inner channels obtained.4.Research on optimization of process parameters of Selective Laser Melting Processing.Based on the influence of process parameters on the dimensional accuracy,flatness and roughness of the formed parts and the mathematical model established by response surface regression analysis,the gamultiobj function is used as the calculating tool to solve the optimization model,and the Pareto optimal solution set of the process parameters of selective laser melting forming is obtained,which provides a reference for the processing of SLM parts of titanium alloy with inner channels.