Coarsening Behavior Of Particles In A Solid/solid System In High Magnetic Fields

Coarsening process is an indispensable basic research subject.Precipitation strengthening,semi-solid processing,liquid-state sintering,liquid synthesis,inclusions control and other research topics related to materials science,that all need to accurately grasp the changing regular of size of the second phase particles.So a good understanding of the basic laws of particles coarsening process is beneficial of controlling particles coarsening processing and changing the microstructure of materials to improve its performance effectively.A high magnetic field is applied to the a solid/solid binary system in solid state during isothermal annealing in this paper,hoping to control the coarsening behavior of particles in the solid phase through a high magnetic field.In this study,the experiment of isothermal annealing in solid state in high magnetic fields of Mn-Sb eutectic alloy were carried out.The microstructure evolution of the alloy and size and distribution of particles of MnSb were investigated,and the mechanism of high magnetic fields was analyzed.The main findings are as follows:(1)With the extension of the holding time,the eutectic MnSb alloy specimens after isothermal annealing in solid state at OT and 11.5T experienced fragmentation,globalization and the coarsening process and formed the eutectic MnSb microstructure of which MnSb particles consist.(2)Compared with the magnetic field of OT,the MnSb phase fragment seriously during the solid isothermal treatment under the condition of 11.5T.Fragmentation started after isothermal treatment for 45min,and ending after about 120min under high magnetic field;however,the fragmentation and nodulizing of MnSb started between 45 and 60min,and fragmentation,nodulizing ending between 120 and 180min.(3)The coarsening kinetics of the eutectic MnSb phases corresponds to(?).The value of n of equation at the magnetic field of OT is equal to three,as predicted by LSW theory.The size distribution of MnSb particles under this condition resemble the steady-state distribution of LSW theory.The particles coarsening at the magnetic field of OT is mainly diffusion controlled.The average size of particles at the magnetic field of 11.5T increases fast with annealing time.The value of n of equation at the magnetic field of 11.5T is equal to four.This indicates that grain coarsening mechanism have changed.(4)The particles contact and merge in the direction parallel to the magnetic field under the magnetic field.This is due to the magnetic interaction between the particles.And they form chain-like structure along the direction of the magnetic field.Anisotropic diffusion,interaction energy between the poles and magnetoctystaline anisotropy energy result in the change of coarsening mechanism.