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Vol.35, No.10, 1366 ~ 1375, 1997
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| Title |
| Effect of Primary Grain Size on the Grain Aspect Ratio of Mechanically Alloyed Oxide Dispersion Strengthened Ni-Base Superalloy |
| 이정훈 , 박이주 , 백경욱 , 김영길 Jung Hoon Lee , Lee Ju Park , Kyung Wook Paik , Young Gil Kim |
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| Abstract |
| Mechanically alloyed (MA) oxide-dispersion-strengthened(ODS) Ni-based superalloy attract great attention as advanced high temperature materials, because they can retain useful strength up to a relatively high fractions of their melting points. Production of a coarse elongated grain structure is very important in MA ODS alloys, since the creep rupture strength is usually increasing with the increasing grain aspect ratio(GAR). The formation of coarse elongated grains is possible during secondary recrystallization by a process of directional zone annealing. The effects of the primary grain sizes on the GAR values of a newly developed MA ODS Ni-Based superalloy, alloy 99, were investigated. The grain structure after zone annealing was strongly depended on primary grain size of as-extruded this alloy. The optimum grain sizes for production a coarse elongated structure ranged from 0.45㎛ to 0.55㎛ in this alloy system. When the primary grain size was less than 0.4㎛, preannealing heat treatment prior to zone annealing brought into the optimum grain size, thereby producing a coarse elongated structure. |
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