| In RS aluminum alloy powders, the surface oxide formed on powders usually contains significant amounts of physically adsorbed water and oxygen. Hence, it is necessary to remove both the adsorbed gas and water from the surface of the powders before consolidation, in order to achieve full density. This removal is usually accomplished by a degassing step. A study has been perfomed on the effectiveness of degassing processes of AC8A alloy powders. Mathematical analysis on the degassing time in the degassing process was done and the factors determining the degassing time were investigated. Computer simulation for degassing process in the powder compact was done considering evaporation, diffusion and reaction. According to the results of simulation, degassing time decreases with decreasing size of powder compact and increasing pore radius. Based on the above results, two method of degassing was performed and compared: static degassing process and dynamic degassing process. The mechanical properties of the specimen made from the dynamic degassing method was superior and its degassing time was much shorter than the other method. |
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