Study On Plastic Behavior Of GH4169 Cutting Zone In High Speed Cutting

GH4169 is nickel-based alloy and is also a multi-component complex alloy.It is widely used in aviation,aerospace and nuclear industries.It has ideal creep resistance,less harmful phase,high temperature oxidation resistance.Despite its excellent high temperature strength,good thermal stability and thermal fatigue resistance,GH4169 has poor cutting processability.There existed complex cutting deformation,higher cutting temperature,higher cutting force,serious tool wears and formation of serrated chip in the process of machining GH4169.Those problems have severely restricted its wide application and have been the focus of attention in the academic and business communities.Therefore,it is of great theoretical significance and wide application value to study the plastic behavior of cutting zone material.It forms sawtooth cuttings during the cutting of nickel-base superalloy GH4169.However,the formation time of every saw tooth unit in serrated chip is very short.It is difficult to use traditional method to analyze the chip at any time.Simulation analysis,integrating with the experimental results,was used to study the whole process of high speed cutting of nickel-base superalloy GH4169.It mainly includes the following research results and conclusions:Firstly,the Johnson-Cook(JC)constitutive model of GH4169 under high speed and high strain rate is established using split Hopkinson pressure bar(SHPB)test.The finite element software(ABAQUS)was used to simulate the whole deformation process in high speed cutting GH4169.Combining the analysis of metallographic pictures which were obtained in the cutting experiment,The process and the formation mechanism of serrated chip were obtained.The results showed that the temperature of local materials in the cutting zone increased rapidly.The appearance of thermal softening of materials led to the change of stress distribution in cutting zone.The thermoplastic shear instability further appeared,which resulted in the shear localization.The shear localization led to the uneven deformation of chip and then serrated chip formed.Secondly,the microstructure and evolution of the adiabatic shear zone were studied,and the crack formation mechanism was further studied.It can be obtained that: adiabatic shear bands exist in two forms,deformation bands and transition bands.The formation process of serrated chip is studied deeply by observing the microstructure of the chip and combining the flow stress of the material under different temperature and strain rate.Based on the flow stress of the material deformation zone and the transition zone in the cutting process,the hardening model of the deformation zone material with the strain is established,and the hardening condition is dominated.Based on the Avrami equation,the kinetic model of the dynamic recrystallization in the transition zone was established.Finally,the stress triaxiality and Lode angle were introduced to reveal the relationship between different cutting conditions and fracture,and the fracture failure behavior of GH4169 in the process of chip formation was studied.