The Research On Deformation Behavior And Critical Grain Growth Of Extruded FGH4096 Alloy

The hot flow behavior and microstructure evolvement regularity of powder metallurgy FGH4096 superalloy is studied in this paper by hot compression test.The constitutive equation and hot processing map of the alloy is established.The machinability and corresponding micro-deformation mechanism is analyzed in order to obtain the optimum range of hot working process parameters.Compression simulation of double conical table specimen is conducted and optimized.The microstructure of compressed hot extruded FGH4096 after solid solution treatment is analyzed and critical grain growth is observedThe change rule of flow stress for the extruded FGH4096 superalloy in hot compression deformation is discussed through the true stress-strain curve obtained by hot compression test.The dynamic relationship between the material parameters such as the hot deformation activation energy and strain is established.The constitutive equation of hyperbolic sinusoidal function with Z value of Zener-Hollomon parameter is established.The calculation results show that the coincidence between the actual test value and the predicted value is high.The relative average error is 8.7%and the correlation coefficient is 0.97%.The equation can provide an accurate prediction of actual stress value for the extruded FGH4096 superalloy in different strain rates,deformation temperatures and strain variables.Based on the dynamic material model,the.processing map composed'by the power dissipation map and the instability map is constructed.The peak region of energy dissipation efficiency combining with corresponding microstructural analysis at the true strain 0.6 is safe region,and the instability parameter ?(?)greater than zero.The optimum range of hot working process parameters in the hot compression deformation for the extruded FGH4096 is established:deformation temperature 1049?1080?,strain rate 0.005?0.013s-1.The energy dissipation rate reaches 64%and complete dynamic recrystallization is occured in this rage,and the grain size is fine and uniform.Numerical simulation for the double conical table specimens is conducted in Deform.The geometry size of double conical table specimens is designed and optimized according the distribution characteristics for the field volume of the equivalent effective strain and the equivalent effective stress in high temperature compression and the actual loading conditions of the compression equipment.The critical dimensions are defined.It is found that average grain size for the extruded FGH4096 superalloy by oversolution treatment after hot deformation in deformation temperature 980? decreased with the increasing of strain rates in equivalent strain range 0.004?0.043.The critical grain growth is occured in strain rate 0.003s-1.The average grain size for the extruded FGH4096 superalloy by oversolution treatment after hot deformation in strain rate 0.03s-1 increased with the increasing of deformation temperature in equivalent strain range 0.004?0.043.The critical grain growth is occured in deformation temperature 1060?.