Mechanical Behavior And Microstructure Evolution Of Zirconium Alloy Sheet During Hot Deformation

The zirconium alloy is widely used to the fuel cladding tubes and positioning grids because of its excellent nuclear capability and good all-round capability,one of the zirconium alloy,the Zirlo zirconium alloy,are noticed and applied extensively because of its advantage that it can markedly reduce the cost of the nuclear fuel and its excellent corrosion resistance property.The Zirlo zirconium alloy rolling plate sample is used as the row material in this article to do the single channel isothermal heat compression experiment with constant strain rate by using the Gleeble-3800 thermal simulation experiment machine.To determine the true stress-true strain curve of the Zirlo zirconium alloy,the deformation temperatures are 550?,600?,650? and 700? respectively,and the strain rates are 0.01s-1,0.1s-1,1s-1 and 10s-1 respectively.The true stress-true strain curve did the temperature rise correction after the experiment.Based on the corrected curve,the flow stress and microstructure evolution influence law of the thermal deformation process of the Zirlo zirconium alloy that impacted by the temperature and the strain rate are analyzed.With the temperature increasing and the strain rate decreasing,the dynamic recovery and dynamic recrystallization of the alloy are reinforced,which caused the increase of the deformation softening and the stress-strain curve is transformed from work hardening curve to the dynamic recovery and dynamic recrystallization curve.Peak stress model of the alloy,modified Arrhenius rheological stress constitutive model that the strain compensation was added in and the segmented constitutive model that combining with the dislocation density evolution of strain hardening and the way of the phenomenological softening was established,the results showed that the strain compensation Arrhenius constitutive model is not suitable for forecasting the alloy that the changing trend of the stress are different with the increase of the strain,and the segmented constitutive model can well predict the flow stress of the Zirlo zirconium alloy under different deformation conditions,which has the advantages of high accuracy,good continuation,using few parameters,and simple calculation,etc.The thermal processing drawing of the Zirlo zirconium alloy was established and the result presented that the best thermal processing parameters are:580?680? for deformation temperature and 0.01s-1?0.05s-1 strain rate.The range of the best parameters is located in the steady state processing range and has the highest energy dissipation rate.The Zirlo zirconium alloy that is thermal processed by applying the parameters above is much easier for alloy to generate the better microstructure and better property.By using the way that flow stress curve combined with microstructure,dynamic recrystallization model of the Zirlo zirconium alloy material was established with verification.The Zirlo zirconium alloy material model that combined with peak stress model and dynamic recrystallization model was integrated into the Deform finite element simulation software to process the zirconium alloy plate rolling processing simulation that using the cloud chart and the points tracking method to analyze the stress,the strain,the temperature distribution of different locations of the rolling plate and the microstructural evolution of the plate in the rolling process.