Prediction Of Solidification Path And Carbide Precipitation Behavior In Fe-C Based Multicomponent Alloy System

The solidification path is a link between macroscopic transmission and microscopic nucleation.Multi-alloy coexistence in the solidification process heterogeneous phase,there is a complex relationship between the various phases,the need to calculate the coupling thermodynamic equilibrium can be solidified path.The Lever Rule(LR)and the Gulliver-Scheil model assume the extreme case of elemental diffusion.the Partial Equilibrium solidification approximation(PE)distinguishes the diffusion of different types of elements in the solid phase.the Para Equilibrium approximation(PA)further considers the solid-solid transformation process.The combination of the Partial Equilibrium solidification approximation(PE)with the Para Equilibrium approximation(PA)or the Partial Equilibrium solidification approximation(PE)with the Lever Rule(LR)predicts the actual solidification path from the liquid phase to the room temperature for the multicomponent alloy.To improve material properties and provide support to new alloy.In order to improve the properties of Fe-C multi-element alloys and understand the precipitation rules of the alloy phases and carbides from liquid phase to room temperature,a model of the Partial Equilibrium(PE)and the the Para Equilibrium approximation(PA)and the Lever Rule(LR)The model predicts the precipitation of carbide in Fe-C multi-element alloys.The main findings are as follows:1.The developed PE+PA model and PE+LR model can predict the whole solidification path of Fe-C-Mn-S-Si-P-Al alloys.(1)The prediction results are in good agreement with the experimental measurements and the predictions in the literature,and verify the reliability of PE+PA model and PE+LR model.(2)The ?-BCC??FCC peritectic transformation process changes after a period of temperature,the ?-BCC phase and y-FCC phase components corresponding changes:?-BCC phase and y-FCC phase C content decreased while the Mn content remained essentially unchanged.(3)The ?-FCC??-BCC solid-solid transformation below the solidus is completed within a certain temperature range.The trends of FCC?BCC solid-solid transition predicted by PE+LR and PE+PA are consistent.2.In view of the carburizing process of automobile gear steel(JIS SCr420),the PE+PA+LR model was used to predict the solidification path of alloy.The model is used to research the solidification path and the carbide formation properties of alloys and the effect of adding V and Ti elements.(1)After carburizing,the carbon content of the alloy gradually increased from the base to the surface.Carbide increase the surface hardness.(2)Alloy generate higher hardness M6C,(Mo,V)C,(Mo,Cr,Fe)3C due to the addition of V.The amount of alloy carbide is small,surface hardness will be slightly increased.(3)Alloy generate higher hardness carbide of M6C,(Mo,Cr,Fe)3C and MC due to the addition of Ti.Total amount of carbides generated by the alloy is less than that when no element is added,and the overall Vickers hardness index remains basically unchanged.