Research On Producing Semi-solid Slurry By Electromagnetic Stirring

Producting closed grained and nearly spherical semi-solid slurry, upgrading the wettability between reinforced particles and liquid metal melt and the uniformly distribution of the reinforced particles are the keys to product metal matrix composites. The process of the semi-solid slurry ,the pretreatment of the reinforced particles ,addition methods of particles and the solid composite technology of electromagnetic stirring are researched in aim of producting semi-solid slurry.From the investigation on producting semi-solid slurry , we learn that the stirring electric current ,stirring frequency ,stirring time has exert same influence on the semi-solid microstructure whether hypothermia or isothermal stirring, nothing but ,hypothermia is better than that one .With the increasing of the current ,the microstructure become parvo , spherical ,uniform. And with the increasing of the frequency ,the microstructure diameter decreases at beginning and it begins to increasing at some limit frequency . It gets most parvo when frequency is 6Hz. On the contrary ,with the accumulating of stirring time, the particles microstructure diameter reduces at beginning and then it begins to increasing .Passing 25min ,it gets most parvo and nearly spherical .The study of the SiC particles addition methods shows that middle addition is better than top addition and bottom addition ,it makes particles interfuse into melt easily when we product composite . It is the best way, using middle addition ,that particles coating Cu ,vacuum-packaged with aluminum foil and preheating to 200oC, is impressed into melt .The invesigation on pretreatment of SiC particles shows that the surface modification of the SiC particles including coating Cu ,drying treatment and high temperature oxidation , coating Cu makes SiC particles interfuse into melt easily and distribute well.When the particles addition method and pretreatment are determined , from the study of producting semi-solid composites with electromagnetic stirring ,we learn that ,on one side ,the uniformity of particles is increasing with the increasing of electric current .The uniformity gets peak when the current is 550A. On another side ,with the increasing of the stirring frequency the uniformity increases at beginning and then it begins to reduce at some a limit frequency. It reaches the peak when start stirring at 660℃and frequency is 6Hz.