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http://dx.doi.org/10.4150/KPMI.2021.28.4.317

Measurement Method of Prior Austenite Grain Size of Nb-added Fe-based Alloys  

Ko, Kwang Kyu (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU))
Bae, Hyo Ju (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU))
Jung, Sin Woo (Materials Science & Engineerings, Dept. of Metallurgical and Materials Engineering, Gyeongsang National University (GNU))
Sung, Hyo Kyung (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU))
Kim, Jung Gi (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU))
Seol, Jae Bok (Department of Materials Engineering and Convergence Technology, Gyeongsang National University (GNU))
Publication Information
Journal of Powder Materials / v.28, no.4, 2021 , pp. 317-324 More about this Journal
Abstract
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).
Keywords
Prior austenite; Grain size; Nb effect; Picric acid etching; Nital etching;
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