Hot Deformation Behaviors And Processing Parameters Optimizing Of Laves Phase NbCr₂/Nb Two-phase Alloy

Laves phase NbCr₂/Nb two-phase alloy is one of the most potential high temperature structural materials.At present,there are few studies on the hot deformation behavior and processing map of Laves phase NbCr₂/Nb two-phase alloy prepared by mechanical alloying and hot pressing sintering process.In this paper,the flow stress-strain curves of Laves phase NbCr₂/Nb two-phase alloy were obtained by compression experiment under the condition of deformation temperature at 800?,850?,900?,950?,1000?,1050?,1100?,1050?,1200? and strain rate at0.1s^-1,0.01s^-1,0.001s^-1.The influence of deformation temperature and strain rate on the flow stress was studied by the rheological curves of Laves phase NbCr₂/Nb two-phase alloy under different deformation conditions.Under the same deformation conditions,the flow stress of Laves phase NbCr₂/Nb two-phase alloy decreases with the increase of deformation temperature or the decrease of strain rate.In the range of experimental parameters,the yield strength of the alloy changes greatly and the steady flow phenomenon appears when the deformation temperature varies from 1050? to1200?.However,the yield strength of the alloy changes smaller and the rheological softening phenomenon occurs when the deformation temperature varies from 800?to 1000?.Based on Arrhenius equation and BP artificial neural network,two kinds of constitutive model of Laves phase NbCr₂/Nb two-phase alloy have been constructed respectively.Comparison of the prediction accuracy of two constitutive model,the average relative error of constitutive model based on Arrhenius equation is more than15%,and the data whose error is less than 10% accounts for 64.09%.However,the average relative error of the constitutive model based on BP artificial neural network is less than 5%,and the data whose error is less than 5% accounts for 98.09%.The results show that the BP neural network method is more accurate than the Arrhenius equation,and it is more suitable for establishing the Laves phase NbCr₂/Nb two-phase alloy constitutive model.Based on the Murty criterion and Prasad criterion of dynamic material model,two kinds of processing maps of Laves phase NbCr₂/Nb two-phase alloy are established respectively.The results shows that the two processing maps of Lavesphase NbCr₂/Nb two-phase alloy are approximately the same.Therefore,the deformation parameters of NbCr₂/Nb two-phase alloy are optimized by superposition of the two processing map.So,the process parameters of Laves phase NbCr₂/Nb two-phase alloy are optimized by overlying the Murty criterion and Prasad criterion.It shows that the stability zone of Laves phase NbCr₂/Nb two-phase alloy is deformation temperature of 1134-1200 ? and strain rate range of 0.001-0.01s^-1.While,the flow instability occured at five regions,800-814? with 0.001-0.1s^-1,914-998? with 0.001-0.1s^-1,996-1108? with 0.006-0.1s^-1,1022-1082? with0.001-0.0021s^-1 and 1114-1187? with 0.019-0.1s^-1.Generally,the best plastic processing zone of Laves phase NbCr₂/Nb two-phase alloy should be controlled under the following deformation condition: the deformation temperature beyond 1130? and strain rate below 0.01s^-1.