京都大学 · 工学
Myeong-heom Park教授の研究室では、高強度鋼の微細組織制御とその力学的挙動の解明を柱として、特に双相鋼（DP鋼）における微細組織の最適化が強度と延性の両立に与える影響を、高精度なデジタル画像相関（DIC）法や微細組織解析を用いて研究しています。特に、フェライト相のナノ・マイクロ構造化とマルテンサイト相の制御を通じて、大規模な工業的応用に適した高強度で延性に優れた鋼材の開発を目指しています。また、超微粒子化されたフェライト組織の形成メカニズムや、反復熱処理と冷間加工を組み合わせた新規プロセスの開発も進んでいます。
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Dual-phase (DP) steel, composed of soft ferrite and hard martensite, is well-known advanced high-strength steel (AHSS) because of its exceptional strength-ductility balance and low manufacturing cost. The present study found that microstructural refinement of DP steel enhanced not only its yield strength but also strain-hardening, leading to increasing both strength and ductility. Digital image correlation (DIC) analysis showed that strains were localized much more in soft ferrite than in hard m
It is well-known that grain refinement is one of the most effective ways to improve strength of metals without addition of alloying elements. In order to obtain bulky metals having ultrafine grained (UFG) microstructures with average grain sizes smaller than 1 μm, severe plastic deformation (SPD) processes have made a great success. However, there are still big barriers to realize UFG metallic materials, especially UFG steels, in large scale industries, since severe plastic deformation processes
Grain refinement in metals is well-known as one of the most effective methods to enhance their strength without addition of other elements. In this study, repetitive heat treatment combined with subsequent cold-rolling and recrystallization were investigated to obtain ultrafine-grained ferrite. Ultrafine-grained (UFG) ferritic structure having a mean grain size smaller than 1 μm was fabricated by repetitive heat treatment at 810 °C for 180 s and cold rolling by 90% plus a recrystallization heat
Dual-phase (DP) steels, consisting of soft ferrite and hard martensite phases, are widely utilized for their favorable balance of strength and ductility. Grain refinement in DP steels has been recognized as an effective strategy to enhance strength without sacrificing ductility, particularly in the post-uniform elongation regime. In the present study, the underlying mechanism responsible for improved post-uniform elongation through grain refinement was investigated using high-resolution digital
Abstract Low carbon dual-phase (DP) steels composed of soft ferrite and hard martensite have been widely used in the automotive industry due to their good strength-ductility balance and large strain hardening ability. DP steels have a wide variation in mechanical properties depending on several microstructural features such as grain size, phase fraction and distribution. Among them, the grain refinement of DP steels is known to be an effective option for enhancing mechanical performance in stren
The microstructures of an Al-Mg-Ga cast alloy have been investigated to fundamentally understand its hardening response during heat-treatment. In as-cast, solution heat-treated, and aged conditions, the alloy is characterized by having a variety of metallurgical phases with unique morphologies and chemical compositions. Micro-hardness indentations subsequent to artificial aging between 50°C and 300°C revealed that the investigated Al-Mg-Ga alloy is capable of Vickers hardness values in excess of
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