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RISS 인기검색어
- 검색키워드
- 저자 : Hojun Gwon (검색결과 2 건)
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Hot Deformation Behavior of V Micro‑Alloyed TWIP Steel During Hot Compression
Hojun Gwon,Sunmi Shin,Jongbae Jeon,Taejin Song,Sungkyu Kim,Bruno C. De Cooman 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3
High manganese twinning induced plasticity (TWIP) steel is an attractive material for automotive applications as its usecould result in an improved vehicle fuel efficiency and a superior passenger safety. Due to the limited research on the hotdeformation behaviour of High Mn steel, the selection of suitable operating conditions for the hot rolling process is challenging. The present contribution focusses on the hot deformation behaviour and the dynamic recrystallization kinetics of Vmicro-alloyed high manganese TWIP steel, by means of single-hit compression test in the temperature range of 850–1000 °Cand the strain rate range of 0.1–10 s−1. The activation energy for hot deformation and the processing map of a V-free TWIPsteel and a V-added TWIP steel were compared by analysing their stress–strain curves. The V-added TWIP steel exhibiteda higher activation energy than the V-free TWIP steel, i.e. 383.4 kJ/mol versus 372.5 kJ/mol. Processing maps based ona dynamic material model indicated that the hot workability of TWIP steel was decreased by micro-alloying with V. Theeffect of V on the hot deformation behaviour of TWIP steels was also analysed by means of its effect on the microstructureusing the SEM-EBSD technique. The V-added TWIP steel was characterized by a higher peak stress at a lower peak strainas compared to the V-free TWIP steel, indicating that the onset of dynamic recrystallization was accelerated by the additionof V. The rapid dynamic recrystallization kinetics resulted in a smaller recrystallized grain size in the hot deformed microstructureof the V-added TWIP steel.
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Suppression of Coating Layer Crack by Diffusion Heat Treatment in Al-Si Coated HPF Steels
Sang‑Man Yun,Hojun Gwon,Jinkeun Oh,Sung‑Joon Kim 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.11
The effect of diffusion heat treatment (DHT) on the cracking of the coating layer in Al-Si coated hot press forming (HPF)steel was investigated. Cracking-induced micro-delamination in the coating layer has limited applications of the Al-Si coatedHPF steels. Introduction of DHT process can modify the microstructure and constituent phase in the coating layer whichcan reduce the cracking. DHT was performed at 650 °C for 360 min to drive Fe diffusion into the coating layer. Formationof band-shaped τ1-Fe3Al2Si3 in the coating layer during the DHT was observed by EBSD and SEM. After HPF process ofthe diffusion heat treated coating specimen, the phase fraction of FeAl increased and that of η-Fe2Al5 decreased comparedto the conventional Al-Si coating specimen, due to the increase of τ1-Fe3Al2Si3. Owing to the higher fracture toughness ofFeAl compared to η-Fe2Al5, application of DHT improved the toughness of the coating layer and reduced the crack densityin it. DHT did not significantly affect the mechanical properties of the base steel.
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