Analysis Of Microstructure Evolution During Liquid Phase Sintering Of Cu-Co Under High Magnetic Field

In the process of liquid phase sintering,the obvious atom convection and diffusion make the particles coarsen obviously,and the pore problem will inevitably appear in the process of liquid phase sintering.Therefore,particle coarsening and pore growth become the core problems in liquid phase sintering process.In order to study the coarsening behavior of alloys during liquid phase sintering,a control method of high magnetic field is proposed.The coarsening behavior of Cu-Co alloy system in liquid phase under high magnetic field was studied.The coarsening and coalescence of its second phase particles were studied,and the behavior change of pore was analyzed.The main results are as follows:(1)By analyzing the morphology of the alloy particles,it is concluded that the coarsening degree of the particles increases with the increase of solid volume fraction or the application of strong magnetic field.When the high magnetic field is applied,the particles distribute in a chain shape along the direction of the strong magnetic field,and with the increase of solid volume fraction,the chain phenomenon of particles decreases.In addition,no matter whether the high magnetic field is applied or not,the particles or the pore are merged,and under the action of the high magnetic field,the pore is distributed along the direction of the high magnetic field.There is a competitive relationship between solid volume fraction and the effect of high magnetic field on the chain distribution of particles.It was found that the coarsening process of Cu-Co alloy resulted in the coalescence mechanism of particle rotation and the coalescence mechanism of particle dissolution-reprecipitation.(2)Through the analysis of particle size distribution and coarsening rate,it is concluded that with the increase of solid volume fraction,the peak value of particle size distribution shifts to the right and the coarsening rate increases.Because particle diffusion coarsening can be divided into two ways:particle contact coarsening and particle dispersion coarsening,the growth rates of particles in the two ways are different.Under the same conditions,the contact coarsening rate of particles is higher than that of dispersed particles.The contact coarsening rate of particles increases with the increase of solid volume fraction,and the contact coarsening rate of particles also increases with the increase of solid volume fraction.In addition,with the increase of solid volume fraction and the increase of holding time,the dihedral angle between particles and particles tends to decrease,and the dihedral angle tends to decrease when the high magnetic field is applied.(3)When the solid volume fraction of the alloy is different,the solute distribution around the particles is also different.When the solid volume fraction is low,the solute concentration gradient around the particles in the alloy system is larger;when the solid volume fraction is high,the solute distribution around the particles is more uniform because of the small spacing between the particles.In addition,the study shows that the flattening phenomenon occurs at the grain boundary because the solute concentration gradient at the phase boundary is quite different from that at other places.