Effect Of Mo On Bainite Precipitation And Structure Property Of V-N Microalloyed Steel

Microalloyed steel has received increasing interest,for its high strength and good toughness,which offers it potential applications in a broad range of industries,such as aviation,automobile and energy field.The high temperature deformation behavior and the low temperaturep recipitation behavior of the V-N-Mo series microalloyed steel were studied,and the effect of the Mo element on the VC precipitation was also examined.At last,Experimental steel was tested in laboratory and its structure and properties were also examined.The results are as follows:(1)The deformation behavior experiment of high temperature austenite shows that the Mo element can restrain the recrystallization and improve the deformation resistance of the steel at the same time.The thermal deformation equation shows that the activation energy of recrystallization can be increased by addition of Mo element,and the deformation resistance model is established,which agrees well with the experimental results.(2)The results of CCT curves show that the addition of Mo can reduce the transformation temperature of ferrite,retard the transformation of ferrite and pearlite,and make the bainite phase shift to the right.Which is advantageous for obtaining bainitic steels.(3)The precipitation behavior of the bainite region shows that the equilibrium precipitates of the precipitates increase significantly with the increase of Mo content,but the precipitation process is also delayed.(V,Mo)(C,N)precipitates mainly through the intergranular diffusion way.In the high-Mo steel,two precipitates appear,of which the rod-like mainly contains V and less Mo,and the spheroidal precipitates mainly contain Mo.With the increase of the isothermal time,the amount of precipitation in each temperature condition increased.After the isothermal 40min,the amount of precipitation is 600?>500?>700?.Mo has obvious inhibition effect on VC precipitation at isothermal 5 min,and Mo can increase the amount of VC precipitation with the isothermal time extended to 40 min.(4)The first-principles calculations show that the incorporation of Mo into the VC can introduce vacancies,vacancies and Mo atoms can reduce the VC formation energy,increase its stability;increase the lattice constant and improve the misfit between VC and the matrix.The interface energy of VC can be reduced significantly.(5)The experimental results of VN-Mo steel show that the strength of Mo steel can be improved obviously by addition of Mo,which has little effect on the toughness of Mo-steel.The structure of VN steel holding at 550? is bainite+ferrite which is tend to roughness with the time prolong.After adding Mo element,the microstructure of the steel is bainite at the final cooling temperature of 550? and no obvious coarsening phenomenon?...