An Investigation On The Atomization Principle And Process Of Molten Metal And Alloy With Solid Powder Medium

Two-fluid atomization of molten metal, in which molten metal is directly crashed into droplets by a high velocity gas stream and then rapidly solidified into powders, is one of the most important methods for the preparation of powders. Numerous researchers have been conducted on it and developed a vast amount of two-fluid atomization processes have been developed since it was invented in 1920s. However, there has been nearly no report on changing the atomization medium. A self-invented, novel atomization process, termed as solid atomization, in which molten metal is atomized into powders by a high velocity gas stream carrying solid particles as the atomization medium, is introduced in the paper. Systematic investigations on the mechanism and the regularties of this process have been conducted by the financial support of the National Natural Science Fund Project and the Doctoral Fund of Education Ministry, and a number lot of significant results have been obtained. The main points are listed as followes:1. The characteristics of powders prepared by common gas atomization and solid atomization under similar conditions have been compared and the effects of the key process parameters on the peculiarity of solid-atomized powders have been systematically studied. The experimental results show that the solid-atomized powders are characteristic of an average particle size one half smaller than that of the common gas-atomized ones, finer microstructure and higher cooling rate under the same atomization gas pressure and the same gas flow. The cooling rate of the solid-atomized powders is one magnitude lower than that of the conventional gas-atomized ones. Similar to gas atomization, the average particle size of the solid-atomized powders decreases with the atomized gas pressure increasing and the molten metal flow reduced. However, the decrease in the solid-atomized powders size is more significant than that of the gas-atomized ones. With the mass flow rate of solid particles increasing, the average particle size of the as-prepared powders decreases at first and then increases. In other words, an optimal atomization effect can be achieved at a proper mass flow rate of solid particles.2. By virtue of high speed photographs, the interactions of high-velocity solid...