A Study On Interactions Between Magnetic Domain Structures And Defects In Fe-V Alloy During High-temperature Creep Deformation

For alloys served under high temperature conditions,high temperature strengthening has always been a focus of research.For existing high-temperature materials,obstructing dislocation movement to improve the high-temperature strength of the material is one of the effective methods.However,none of the existing studies have revealed from the microscopic perspective that the mechanism of magnetic influence on the dislocations in the material and the movement of defects such as grain boundaries increases the high-temperature creep strength of the material.In this article,Fe-12%V alloy was taken as the research object to study the creep stress sensitivity and creep mechanism at the creep rate,and observe the dislocations,grain boundaries,and sub-alloys in the alloy under different creep experimental parameters(temperature and stress).Distribution of defects such as grain boundaries and small-angle grain boundaries,analysis of the distribution characteristics of microscopic magnetic structure in the alloy and its influence on microscopic defects,and discussion of the interaction between magnetic domains and defects in the alloy during the Fe-V combined high temperature creep process Law of action.The findings are as follows:1.In Fe-V alloys,due to the paramagnetic characteristics of V,the addition of V element results in a decrease in the degree of magnetic order in Fe-V alloys,resulting in a large change in the steady-state creep rate before and after the Curie point,and the magnitude of the change up to 108 orders of magnitude.2.Under the condition of 780℃ creep experiment,the calculated stress index of Fe-12%V alloy is 5.19.The creep mechanism of the alloy is mainly dislocation movement.As the stress increases,the micro strain in the alloy increases.No significant change in grain size and dislocation density.The magnetic domains in the alloy widen with increasing stress,the magnetic domain walls are refined,and the distance between the magnetic domain walls increases.At the same time,the magnetic domain wall undergoes bending deformation at the dislocation plug.As the stress increases,the degree of bending of the magnetic domain wall increases,and the pinning effect of the magnetic domain wall increases.3.When the creep of Fe-12%V alloy between 530℃ and 780℃,the thermally activated movement of dislocation movement intensifies with increasing temperature.In the ferromagnetic state,dislocation plugs exist at the bends of the magnetic domain walls.Product and grain boundary broadening,due to the interaction of the atomic magnetic moment and the elastic strain field of dislocations,the dislocation entanglement movement is hindered,and a large number of entanglements and intersections occur at 780℃;as the temperature further increases to the Curie point Above,the dislocations apparently recovered and annihilated,but the formation of small-angle grain boundaries and sub-grain boundaries was observed in the grain boundaries.At this time,the creep mechanism changed from dislocation motion to grain boundary motion.As the creep temperature increases,the magnetic domains broaden.4.When the temperature is 830℃,the orientation of the magnetic moment of the atoms tends to be disordered,the constraint of magnetic domains with different orientations is weakened,and the domain transition occurs in the closed domain.The magnetic domain structure in the Fe-V alloy changes from a closed-flow magnetic domain structure to a lamellar magnetic domain.structure.