γ鉄の焼結機構の一考察

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The sintering mechanisms of gamma iron had been examined from the neck growth experiment on spool model compacts by Fischmeister and Zahn, and Matsumura, respectively. Both groups found that the neck growth exponent changes from 5 at high sintering temperature to 7 at low temperature and concluded that volume diffusion mechanism prevails at high temperature and surface diffusion controls the process at low temnerature.<BR>In the sintering experiment of nickel on various model compacts, however, Ichinose and Igarashi found that the neck grain-boundaries in spool model compact are not effective sink for vacancies, which may be attributed to strong restriction to shrinkage in this model compact.<BR>From this point of view, a sintering experiment of gamma iron was conducted on 3 wire model compact, in which neck growth and shrinkage were observed as a function of time at 1300°, 1200°, 1100° and 1000°C. The corresponding exponents were 5, 5.5, 6.2 and 7, respectively. Shrinkage was observed in the sintering at high temperatures, but not observed at 1000°C, except long time side. The volume diffusion coefficients obtained from neck growth and shrinkage at 1300°C coincide with each other and are in fairly good agree-ment with tracer results. The surface diffusion coefficient obtained from neck growth at 1000°C was in fairly good agreement with Matsumuras result. Thus, in this three wire model compact, volume diffusion with vacancy sink at neck grain-boundaries prevailed at high temperature and surface diffusion did at low temperature.
社団法人粉体粉末冶金協会の論文

γ鉄の焼結機構の一考察

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