Study On Effect Of Hot Deformation On M₂C Alloy Carbide Phase Transition In High Speed Steel

High speed steel is the raw basic material in the field of mechanical manufacturing,and it is widely used in manufacturing various kinds of cutting stools,high load moulds.Due to the component,microstructure and technology characteristic,high speed steel is very easy to produce the main characteristic quality problem that large and unevenly distributed carbides.How to refine the size of bulk carbides and obtained the smaller,evenly distribution tissues,is an important technical problem to prepare high quality high speed steel.The text investigate the influence of compression variables and the deformation temperature on the microstructure evolution,M₂C alloy carbide phase transition behavior and mechanism.Focus on studying strain enhance the M₂C carbide phase transition and thermodynamic and kinetic behavior in high speed steel,which have been investigated by Gleeble-3800 thermal simulator,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）.The effect of compress vibration on the M₂C alloy carbides phase transition.The results show that the inner M₂C carbides produce the dislocations and stacking faults after deformation.with improving the compression ratio,the density of dislocations are gradually increases.Hot compression deformation enhance the M₂C alloy carbide phase transition,the carbides phase variables increase as the compression strain increases.The new phase generation position extended from the M₂C carbide/the interface edge to the interior of M₂C carbide.Due to the uneven deformation,high density dislocation areas are benefit for generating the new phase.It is the cause of deformation enhances carbide phase transition.The influence of temperature on the M₂C alloy carbide transition was investigated.The results show that with increase the temperature,the more new phase are generated.The effect of the deformation enhanced carbide phase transition increases with the increase of the deformation temperature and then decreases,depending on the dominant role of the dislocation density and the atomic diffusion rate at different temperatures.Among them,it is the most significant change that deformation enhanced carbide phase transition at 1050℃deformation.The M₂C carbide phase transition kinetics was studied.Based on the Johnson-Mehl-Avarmi equation,M₂C alloy carbide phase transition kinetic equation was established as well as the hot deformation activation energy,undeformed and 40%compression deformation.which E₀=8.62*10⁵J and E_0.4=5.71*10⁵J respectively,Avarmi value-n are 1.74 and 1.38 respectively.Deformations can reduce the activation energy of carbide transition,and it is correspond to the inner M₂C carbides produce the dislocations and stacking faults after deformation.According to the carbide phase transition of Avarmi value,the M₂C eutectic carbides phase transition is a one-dimension diffusion mechanism.