High Temperature Creep Behavior And Microstructure Analysis Of Fe-V Alloys

High temperature service performance of materials have been much attention of researchers,especially creep resistance.Some researchers have suggested that magnetism impact on the creep strength of the material.The plastic deformation of the material depends on the dislocation movement,and it is an effective way to improve the high temperature strength of the material that the dislocation movement be blocked.Our group has studied the magnetic properties and mechanical properties of Fe-V alloys and found that the magnetic properties of Fe-V alloy changed with the increase of content and temperature of V,and the yield strength mutation at curie temperature in Fe-12 at.%V alloy.However,previous studies did not reveal how magnetic influences the dislocation motion and the mechanism of the high-temperature creep strength be improved.The mechanism of the interaction between magnetic domains and dislocations and its effect on the mechanical properties were studied and the effect of the magnetic transition on the creep rate was quantitatively described in Fe-12 at.%V alloy using the machine of RDL-50 slow tensile stress corrosion/creep,DSC,XRD,VSM and L-TEM in the article.The following is results:(1)Under constant stress,the steady-state creep rate(?)in the range of 10-9s-1?10-5s-1 increasing slowly with the temperature increasing below 650?;The ? changes greatly in the range of 10-5s-1 to 10-3s-1 with the temperature from 780? to 880?;When the temperature exceeds 880?,? increases slowly near 10-3s-1 with the increase of temperature,indicating that magnetic transitions have an impact on ?.(2)The magnetic domain of Fe-12 at.%V alloy is smaller and more dense in ferromagnetic state than that of paramagnetic state.The dislocations accumulated in magnetic domain walls in ferromagnetic state,The movement of dislocations are impede due to the interaction between the atomic magnetic moment and the elastic strain field of dislocations in magnetic domains.(3)When the temperature is constant,the steady-state creep rate increases with the increase of applied stress.When the stress is under 20 MPa,? increases like power function increases.When the stress is greater than 20 MPa,?exponentially increases.(4)The atomic magnetic moment of Fe-12at.%V alloy decreases with the increasing of temperature,and the difference of the atomic magnetic moment near the curie temperature point(Tc)is 0.55?B.Both steady-state creep rate and atomic moment showed discontinuous changes and had a negative correlation near the Tc.(5)The relationship between steady-state creep rate ?-1/m and magnetic moment ?/m·ST/S0 is quantitatively described as ?-1/m=Kexp(?/m·ST/S0).The curves of ?-1/m and ?/m·ST/S0 for Fe-12 at.%V alloy with m=4.55,5 are in agreement with the exponential law and with the fitted curves approximate.