Coarsening Behavior Of Particles During Liquid Phase Sintering Process Of Cu-Co In High Magnetic Field

Particle coarsening is the core issues of materials processing like liquid phase sintering,syntheses of hollow nano-materials,semi-solid processing,inclusions control and so on.For the liquid phase sintering process,since its uniform composition,high hardness and high yield strength,it is widely used in the engineering materials preparation,A high magnetic field is applied to the liquid phase sintering process in this paper,and control the coarsening behavior of particles by high magnetic field.In this study,the experiments of isothermal annealing of Cu-Co samples with different solid volume fraction at various temperature in the liquid phase sintering process under high magnetic field were carried out,the microstructure evolution,particle size and distribution of Co particles were investigated,the mechanism by high magnetic field was analyzed.The main findings are as follows:(1)The coarsening process of Co particles in liquid Cu matrix was accelerated by the application of high magnetic field at 12T,and the coarsening rate of particles was increased.The size distribution curve of particles was broadened and the peak moved towards the direction of large size.Co particles came into contact with each other in the direction of magnetic field,and then formed a chain-like structure.At the same time,the high magnetic field had a certain effect on improving the relative density of samples during liquid phase sintering process.(2)With the increase of the sintering temperature,the increasing amplitude of coarsening rate and the alignment degree of Co particles weaken.With the decrease of the volume fraction of Co particles,the degree of the formation of chain-like structure of Co particles increased and the particles elongated along the magnetic field direction.(3)High magnetic field raised probability of contact and coalescence between particles,and coalescence by grain boundary migration occurred in Cu-Co systems with different solid volume fraction.It appeared coalescence by neck growth with the decrease of solid volume fraction,but the probability of occurrence by this coalescence at 12T was not higher than that at 0T.(4)The coarsening kineticL of Co particles corresponded to(?)? t,and it still satisfied diffusion controlled mechanism by LSW theory.Interaction between the magnetic poles,the Lorentz force and energy of magnetic caused by high magnetic field were the main reasons for promoting the coarsening process and formation of the chain-like structure.