Study On High Temperature Deformation Behavior And Processing Map Of Two-phase NbCr₂/Cr Alloy In-situ Synthesis

NbCr₂/Cr two-phase alloy is a novel high temperature structural materials with high melting point,proper density and excellent high temperature strength.Due to the composition of Laves phase NbCr₂ and Cr solid solution,NbCr₂/Cr two-phase alloy not only retains the excellent high temperature mechanical properties of Laves phase,but also has good high temperature oxidation resistance and corrosion resistance.So NbCr₂/Cr two-phase alloy is considered as one of the novel high temperature structural materials with promising application potential.In this paper,the hot deformation behavior of in-situ NbCr₂/Cr two-phase alloy by mechanical alloying and hot pressing was studied in the deforming temperature range of800¹200?and strain rate range of 0.001⁰.1s^-11 through the high temperature compression test.Then,the constitutive model of NbCr₂/Cr two-phase alloy was established which can describe the thermodynamic behavior phase accurately.Finally,the hot processing map of NbCr₂/Cr two-phase alloy was obtained through the optimum forging process parameters of regional structure construction method.From the flow stress curve of alloy,it can be seen that the flow stress of NbCr₂/Cr two-phase alloy is decreased with the increase of deformation temperature and the reduction of strain rate.The flow stress of NbCr₂/Cr two-phase alloy is greater than the strain rate.When the temperature is below 1000?,the true stress-true strain curve of the alloy is a flow softening curve.However,When the temperature is above 1000?,the true stress-true strain curve of the alloy is a steady flow curve.The constitutive model of NbCr₂/Cr two-phase alloy was established by respectively using Arrhenius type,stepwise regression method and BP neural network model.Through the error analysis of these three constitutive models,it is found that the Arrhenius constitutive model modified by Z parameter has poor prediction accuracy and its average relative error is 19.51%,which can not meet the requirement of engineering application.The stepwise regression constitutive model with 1000?as the demarcation point has good prediction accuracy.The average relative error of the model below 1000?is 8.08%,and the average relative error of the model above1000?is 6.12%.The prediction accuracy of the constitutive model based on BP neural network is higher and the average relative error is 1.7%.So the stepwise regression method and BP neural network model are suitable for predicting the flow behavior of NbCr₂/Cr two-phase alloys,and the prediction accuracy can meet the needs of engineering applications.The forging process optimization of NbCr₂/Cr two-phase alloy has been studied by using processing map.The hot processing maps of NbCr₂/Cr two-phase alloy under different true strain was established by using the Prasad criterion and the Murty criterion in the dynamic material model.Through the comparison and analysis of the two heat processing diagrams,it is found that the Murty criterion is more accurate in predicting the regimes of instability,predicting the regimes of flow stability and optimizing forging process parameters.The predicted results by using the processing map based on Murty criterion are the following.For NbCr₂/Cr two-phase alloy,the regimes of flow instability are in the temperature and the strain rate ranges of800⁸10?and 0.002⁰.1s^-1,980¹085?and 0.01⁰.1s^-1.The reasonable process parameters for forging are in the temperature ranges and the strain rate ranges of1020¹100?and 0.001⁰.01s^-1,1100¹200?and 0.001⁰.01s^-1.The optimum process parameters are located near 1060?and 0.001s^-1,1150?and 0.001s^-1.