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복합 밀링 공정에 따른 철계 산화물분산강화 합금의 미세조직 및 기계적 특성 변화 연구
설재복 ( Jae-bok Seol ),김경민 ( Kyong Min Kim ),김정한 ( Jeoung Han Kim ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.3
A novel approach is established to produce oxide dispersion-strengthened steels with a fine distribution of oxide nanoparticles. This approach involves cryo-milling followed by ball-milling at room temperature. This complementary milling technique allows such steels to exhibit a remarkable combination of strength and ductility. Based on our experimental findings, the associated microstructural factor contributing to the strength is likely to be Y-Ti-O complex oxide particles. On the other hand, an additional milling process performed at room temperature is not effective with regard to deformationinduced sintering. Therefore, it is concluded that milling at room temperature after cryo-milling does not improve the tensile ductility of oxide dispersion-strengthened steels.
Nb 첨가 철계 합금의 Prior austenite 결정립크기 측정 방법
고광규,배효주,정신우,성효경,김정기,설재복,Ko, Kwang Kyu,Bae, Hyo Ju,Jung, Sin Woo,Sung, Hyo Kyung,Kim, Jung Gi,Seol, Jae Bok 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.4
High-strength low-alloy (HSLA) steels show excellent toughness when trace amounts of transition elements are added. In steels, prior austenite grain size (PAGS), which is often determined by the number of added elements, is a critical factor in determining the mechanical properties of the material. In this study, we used two etching methods to measure and compare the PAGS of specimens with bainitic HSLA steels having different Nb contents These two methods were nital etching and picric acid etching. Both methods confirmed that the sample with high Nb content exhibited smaller PAGS than its low Nb counterpart because of Nb's ability to hinder austenite recrystallization at high temperatures. Although both etching approaches are beneficial to PAGS estimation, the picric acid etching method has the advantage of enabling observation of the interface containing Nb precipitate. By contrast, the nital etching method has the advantage of a very short etching time (5 s) in determining the PAGS, with the picric acid etching method being considerably longer (5 h).