ニッケルの高温焼結の機構(第2報) : 3 tube model とspool modelによる実験

概要

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In order to eliminate neck grain-boundaries, a special 3 tube model compact was prepared. The neck growth behavior was observed on this model compact as well as on ordinary spool model compact. The obtained experimental results were analyzed and compared with those on 3 wire model compact reported in the first paper. The neck growth on 3 tube model compact without neck grain-boundaries follows Kuczynskis 5th power relation for volume diffusion mechanism with vacancy sink at adjacent free surface. The neck growth rate in the scale of x5/a2 (x: half width of neck, a: radius of wire) on 3 wire model compact with grain boundaries was 2.5 times faster than that on 3 tube model compact without grain boundaries, which is close to theex pected value of 2.83. The neck growth rate on spool model compact, in which neck grain-boundaries were present, was the same as that on 3 tube model compact. This implies that grain boundaries in spool model compact are not effective sink for vacancies. The reason maybe due to strong restriction to shrinkage in spool model compact.