Research On The Macro-mesoscopic Mechanical Behavior Of Nickel-based Superalloy Based On Crystal Plasticity Theory

Due to the excellent high temperature mechanical properties,Nickel-based high-temperature alloy widely used in high temperature bearing parts in the field of industrial raw materials,and with such components should be in high temperature,high load and high strain rate conditions such as service,thus to explore nickel base alloy under the certain condition of bearing the relationship between microstructure and properties,has important guiding significance for engineering practice.Based on the theory of Crystal Plasticity,this paper selects nickel-based single Crystal alloy（DD6）and polycrystal alloy（GH4169）as the research objects respectively.Based on the related experimental results,CPFEM（Crystal plastic Element Method）is applied.The mechanical behaviors of nickel-based superalloys with different organization and load conditions were researched.The main contents are as follows:（1）ABAQUS finite element software was used to develop a model of crystal plasticity,and the crystal plasticity parameters of nickel based single crystal and polycrystal were calculated by user subroutines.The results show that the obtained parameters can well formulate the mechanical properties of nickel-based superalloy,and the errors between the calculated results and the experiment are less than 5%.（2）CPFEM was used to research the mechanical properties of DD6 at high temperature under three different orientations of nickel-based single crystal alloy,and the corresponding mechanical response and crystal slip results were obtained.At a temperature of 760°C,the[120]orientations exhibit lower yield and flow stresses due to the different activation of the slip system.The elastic modulus increases with the increase of deflection Angle and is the maximum at[110]orientation.In the process of lateral stretching,the alloy exhibits significant anisotropy due to the different number of activation of slip systems and Schmid factor in the orientation of[100],[120]and[110],and the grains of different orientations rotate around the Z-axis.（3）The mechanical responses of nickel-based polycrystalline alloy GH4169 at different temperatures and strain rates were researched by integrating experiments and CPFEM.At 20℃and 200℃,the alloy exhibits Positive Strain Rate Sensitivity（PSRS）.At 400℃,the alloy exhibits Negative Strain Rate Sensitivity（NSRS）and obvious serrated rheological characteristics.The experimental results at different temperatures and strain rates show that the yield strength of the alloy decreases with the increase of tensile temperature,while the yield strength and tensile strength of the alloy increase at the strain rate of 0.0001s^-1and temperature of 400℃compared with that at200℃,which is caused by the dynamic strain ageing phenomenon of the material microstructure at 400℃.At 600℃,the material does not show the corresponding dynamic strain ageing effect.（4）Building Crystal plasticity model of GH4169 based on EBSD technology.The analysis shows that the acquisition step size of EBSD has a great influence on the evolution of deformed grain,but has low impact on its macroscopic mechanical response.Stress concentration exists at different magnification times,and the stress concentration decreases with the method multiple increasing,while the maximum stress value increases.When the magnification is 400 times,the maximum stress value is 4832.7MPa,and the material model begins to shrink.At different temperatures,the cumulative shear slip strain distribution is roughly the same,and the cumulative shear strain increases with the increase of temperature.After tensile deformation,the orientation evolution of grains in polycrystals is complicated.Besides the z-axis rotation,the diffusion phenomenon related to grain position and stress also occurs.