Grain refinement of dual phase steel maximizes deformation ability of martensite, leading to simultaneous enhancement of strength and ductility

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 martensite but the refinement of DP structure decreased the difference in average strains of ferrite and martensite, which avoided crack initiation in ferrite and led to large ductility. Consequently, the refinement of…

• MO
  Ministry of Education, Culture, Sports, Science and Technology
• KU
  Kyoto University

  Award: 2018B0150
• JS
  Japan Society for the Promotion of Science

  Awards: JP23H00234, JP22K18888, JP20K14608, JP24K07214, JP23K20037
• CR
  Core Research for Evolutional Science and Technology

  Award: JPMJCR1994