Research On Milling Mechanism And Process Parameter Optimization Of Titanium Aluminum Alloy Thin-walled Part

Titanium aluminum alloy is one of the preferred materials for Aeroengine Blades because of its low density,high temperature resistance,good oxidation resistance and flame retardancy.However,titanium aluminum alloy has the characteristics of low plasticity and high brittleness at room temperature,which makes it very difficult to process titanium aluminum alloy,which seriously limits the practical application of titanium aluminum alloy in industrial field.Therefore,based on milling experiments,this paper systematically studies the thin-walled titanium aluminum alloy parts.The main contents include studying the wear morphology and wear mechanism of tools under different milling parameters,studying the effects of milling parameters and cantilever length on milling force and surface integrity,and finally optimizing the milling parameters for machining thin-walled titanium aluminum alloy parts based on NSGA-Ⅱ algorithm.The law of tool wear in milling titanium aluminum alloy was studied.The results show that increasing the milling parameters will shorten the milling distance of the tool.The front and back flank wear of the tool mainly includes bonding wear,oxidation wear and diffusion wear,and there is coating peeling.A tool life prediction model based on milling parameters is established.Through inspection,it is found that the model can meet the general prediction requirements of tool life.The effects of milling parameters and cantilever length on milling force of thin-walled titanium aluminum alloy parts were studied.The results show that the milling force first increases and then decreases with the increase of spindle speed;With the increase of back draft,feed per tooth and line spacing,the milling force increases gradually.With the increase of the cantilever length of the workpiece,the milling force decreases.Among the milling parameters,the back draft has a significant impact on the milling force,followed by the feed per tooth,while the spindle speed and row spacing have a weak impact on the milling force.The milling force model based on milling parameters is established,and the model is verified to have good accuracy.The effects of milling parameters and cantilever length on the surface integrity of titanium aluminum alloy thin-walled parts were studied.The results show that the surface roughness and surface microhardness first increase and then decrease with the increase of spindle speed.The surface roughness and surface microhardness increase with the increase of feed rate per tooth,back draft,line spacing and cantilever length.The depth of plastic deformation layer decreases with the increase of spindle speed and cantilever length,and increases with the increase of feed per tooth,back draft and row spacing.Among the milling parameters,the influence of row spacing on surface roughness is highly significant,the influence of feed per tooth on surface roughness is more significant,and the influence of spindle speed and back draft on surface roughness is weak.A surface roughness model based on milling parameters is established.The process parameters of milling titanium aluminum alloy thin-walled parts were optimized.The optimization models with machining efficiency and machining cost as the objective function in rough machining of titanium aluminum alloy and the optimization models with surface roughness,milling force and machining efficiency as the objective function in finish machining of titanium aluminum alloy thin-walled parts are established respectively.The optimal combination of milling parameters satisfying the corresponding objective function is calculated by NSGA-Ⅱ algorithm.