.403 Of Nb Dynamic Recrystallization And Thermal Deformation Microstructure Evolution

403Nb is a kind of martensitic stain less steel,which is used to make the turbine blade of heat-engine unit.The investigation of the behavior of dynamic recrystallization and the development of microstructure of 403Nb by the experiment of one-pass Hot compression on Gleeble-3500 is the main idea of this thesis and also as one part of basic work of simulation and prediction of the evolution of microstructure and properties of hot rolled steels.Ddependence of dynamic recrystallization on strain rate,strain tempreture and strain capacity is investigated.The true strain capacity is 0.91,the strain tempreture is from 850℃～1150℃and the strain rate is from 0.01S^-1～10S^-1.To collate experimental data,to draw the stress-strain curve by the result of expirement,to analize the regularity,at last,the model of dynamic recrystallization of 403Nb was built.To observe the microstructure after hot compression under metallographic microscop,SEM and TEM,the regularity of development of microstructure was analized.Through out the solid solution experiment,the microstructure and prcipiated phase after hot treatment were investigated,including the species,pattern and size.To generalize the whole thesis,get the follwing conclusions:1.At the same strain rate and different strain tempreture,when the tempreture is higher,the flow stress is stronger and it's easier to start the dynamic recrystallization;At the same strain tempreture and different strain rate,when the strain rate is lower,the flow stress is lower,it's easier to start the dynamic recrystallization;2.It shows that the dynamic recrystallization of 403Nb occurs obviously when the comepression temperature is from 1100℃to 1150℃and strain rate is from 0.01S^-1to 0.1S^-1.When the strain rate is 10 S^-1,only dynamic recovery has occurred;3.The flow stress of 403Nb steel can be represented by a Zener-Hollomon parameter in the hyperbolic logarithm type equation.The Z parameter and regressed peak stress expression isσ_P= 14.5926lnε+1002406.111·T^-1-604.613658. Z=εexp(68696.8968/T)=9.8647×10¹⁰exp(0.06853σ_P)The hot deformation activation energy of 403Nb steel during hot compression is 571.146kJ/mol; 4.Dynamic recrystallization and dynami recovery usually occur at the same time,dynamic recrystallization nuclearation occurs first at inhomogeneous deformation site;5.Compared with strain rate,strain temperature influences dynamic recrystallization more sensitively under the same strain capacity;At 1150℃and 0.01S^-1,the austinate grain begin to grow,the size is from 15～50μm;6.Compared with non-recrystallization microstructure,martensite lathes are more regulate and the borders are clearer;7.A small quantity of residual austenite and twins exist in microstructure after hot compression,the size of twins is small,about 30～100nm,austenite distribute at martensite border as slender chips;8.By the solid solution temperature rising,the strength of 403Nb increased obviously,the precipitated phases are M₂₃C₆ and NbC after solid solution and temper treatment;...