| 7150 aluminum alloy is a high-strength aluminum alloy that has a wide range of applications in fields such as aerospace,aeronautics,and military industry.Its strength and toughness can be improved by heat treatment processes such as solid solution and aging,and its corrosion resistance and fatigue performance can be enhanced,which makes it better suited to meet the requirements of cutting processing.Currently,research on this material focuses on its mechanical properties and heat treatment,with little involvement in the field of processing technology.Therefore,this paper chooses 7150aluminum alloy as the research object and studies the effect of different aging processes on its material properties,milling performance and surface quality.Firstly,a single-stage,interrupted,and re-aging heat treatment was performed on7150 aluminum alloy to obtain T6,T6I4,and RRA states.The effects and advantages of different aging processes on microstructure and surface hardness were investigated.Shorter holding times and lower heating temperatures in the aging process are not conducive to the dispersion and growth of the second phase,while longer holding times can lead to the coalescence of the second phase,which mainly includes Al2Cu Mg and Mg Zn2 phases.The T6I4 alloy exhibits the highest strength,while the RRA alloy has high corrosion resistance due to the formation of a no-precipitation zone.The hardness order of the three alloys is as follows:7150-T6I4>7150-T6>7150-RRA;and the volume fractions of the second phase are 7.6%,12.6%,and 9.7%,respectively.Secondly,the dynamic mechanical properties of aluminum alloys with different aging processes were compared,and a constitutive equation was fitted.During quasi-static compression experiments,heat was generated as the material lattice structure deformed,and lattice defects were generated in local deformation areas,which improved the material’s strength and deformation resistance.Based on the analysis of the dynamic mechanical test results,the Johnson-Cook constitutive equation parameters were fitted.Under high strain rate conditions,the lattice structure of the aluminum alloy changed,making the material more plastic and changing the failure mode to local plastic deformation.The toughness and resistance to failure of the aluminum alloy decreased as the temperature increased.Furthermore,using Abaqus finite element analysis software to build a milling model for simulation research,explore the variations of cutting force and temperature under different processing parameters,and analyze the effect of aging process on milling performance.The maximum cutting force and temperature were found in 7150-T6I4,while the minimum was in 7150-RRA.The cutting force increased and then decreased with the increase of milling speed,and the milling depth and feed rate affected the cutting force through material removal rate and pressure.The maximum stress occurred in the contact area between the front cutting surface and the material during the processing,and it increased first and then decreased with the increase of milling speed,while the equivalent stress increased with the increase of milling depth.The temperature increased with the increase of milling speed and depth,and the highest temperature during the material removal process mainly occurred in the contact area between the tool’s front cutting surface and the workpiece and chips.The chips away from the processing area continuously received the temperature transmitted from the milling area due to the thermal conduction effect.Finally,the validity of the simulation results was verified by machining experiments.The influence of machining parameters on surface quality was analyzed,and the small-wavelet neural PID control algorithm was used to suppress chatter during milling.The experimental cutting force and temperature trends were consistent with the simulation results,and the errors were within the allowable range.Applying the small-wavelet neural network PID control algorithm on the basis of the cutting force model and the tooth dynamics trajectory can effectively suppress chatter during milling,and maintain a lower amplitude at higher processing frequencies after active suppression.The range of workpiece vibration is significantly reduced,making the machining process more stable.Milling speed and feed rate have a significant impact on material surface quality.The trend of surface roughness change is consistent among the three materials,and the size relationship is 7150-RRA>7150-T6>7150-T6I4.Surface quality improves with increasing milling speed and deteriorates with increasing feed rate. |
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