Harmonic structure materials are materials with a core–shell structure having a shell with a small grain size and a core with a relatively large grain size. They are in the spotlight because their mechanical properties reportedly feature strength similar to that of a sintered powder with a fine grain size and elongation similar to that of a sintered powder with a coarse grain size at the same time. In this study, the tensile properties, microstructure, and stretchflangeability of harmonic structure SUS304L made using powder metallurgy are investigated to check its suitability for automotive applications. The harmonic powders are made by mechanical milling and sintered using a spark plasma sintering method at 1173 K and a pressure of 50 MPa in a cylindrical die. The sintered powders of SUS304L having harmonic structure (harmonic SUS304L) exhibit excellent tensile properties compared with sintered powders of SUS304L having homogeneous microstructure. In addition, the harmonic SUS304L has excellent stretch-flangeability compared with commercial advanced high-strength steels (AHSSs) at a similar strength grade. Thus, the harmonic SUS304L is more suitable for automotive applications than conventional AHSSs because it exhibits both excellent tensile properties and stretch-flangeability.

• 윤재익(포항공과대학교 신소재공학과) | Jae Ik Yoon (Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• 이학현(포항공과대학교 신소재공학과) | Hak Hyeon Lee (Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• 박형근(포항공과대학교 신소재공학과) | Hyung Keun Park (Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• KeiAmeyama(Department of Mechanical Engineering, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan) | Kei Ameyama (Department of Mechanical Engineering, Faculty of Science and Engineering, Ritsumeikan University)
• 김형섭(포항공과대학교 고엔트로피합금연구단) | Hyoung Seop Kim (Center for High Entropy Alloys, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea) Corresponding author