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Vol.35, No.8, 935 ~ 942, 1997
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| Title |
| Selective Precipitation of Carbides in Alloy 690 |
| 이용복 , 장진성 , 이덕열 , 이동희 , 국일현 Yong Bok Lee , Jin Sung Jang , Dong Hee Lee , Dok Yol Lee , Il Hiun Kuk |
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| Abstract |
| Precipitation behavior of solution heat treated Alloy 690 tubes (60Ni-30Cr-10Fe: UNS N 06690) has been studied. Carbide precipitates along grain boundary were revealed as M_(23)C_6 type carbide having semi-coherent interface with one adjacent grain. Also drastic change of precipitate density was observed on a twin intercepted grain boundary, i.e, abundant precipitates on general grain boundaries, but no precipitate on boundary segments intercepted by twins. This selective precipitation phenomenon was attributed to the different orientation relationships of grain boundary segments, i.e. different misorientation characteristics, and eventually drastically different boundary energy. Different misorientation characteristics of interfaces were investigated through Kikuchi pattern analyses in TEM. The grain boundary with precipitates was random high angle grain boundary and the clean segment of boundary was CSL (Coincidence Site Lattice) special boundary (e.g. ∑=15), judged by Brandon`s criterion. Of course coherent twin boundary with ∑=3 were free of precipitate. (Received April 2,1997) |
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