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<p>Previous studies indicate that as carbon content increases in bainitic steel, the effect of preformed martensite (PM) on impact toughness shifts from beneficial to detrimental. Although the toughening mechanism is understood, the embrittlement mechanism remains unclear. This study investigates the role of PM in bainitic steel toughness using 0.24C and 0.34C steels. For the 0.34C steel, retained austenite (RA) in PM-containing steel exhibited enhanced stability under quasi-static tension but decreased stability under impact loading. Analysis indicated that the high dislocation density in the PM of the 0.34C steel traps more carbon, while the lower austempering temperature slows carbon diffusion, reducing the carbon content in RA. Under rapid deformation, dislocation blocking weakens the matrix “shielding effect” on RA, reducing its mechanical stability. This instability diminishes plastic energy absorption, consequently reducing impact toughness.</p>

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Detrimental Role of Preformed Martensite on Impact Toughness of Ultra-Fine Bainitic Steel with Elevated Carbon Content

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Wang Qingchao,
  • Wang Helin,
  • Li Hongguang,
  • Su Yinglong,
  • Sun Dongyun,
  • Feng Xiaoyong,
  • Yang Zhinan,
  • Zhang Fucheng

摘要

Previous studies indicate that as carbon content increases in bainitic steel, the effect of preformed martensite (PM) on impact toughness shifts from beneficial to detrimental. Although the toughening mechanism is understood, the embrittlement mechanism remains unclear. This study investigates the role of PM in bainitic steel toughness using 0.24C and 0.34C steels. For the 0.34C steel, retained austenite (RA) in PM-containing steel exhibited enhanced stability under quasi-static tension but decreased stability under impact loading. Analysis indicated that the high dislocation density in the PM of the 0.34C steel traps more carbon, while the lower austempering temperature slows carbon diffusion, reducing the carbon content in RA. Under rapid deformation, dislocation blocking weakens the matrix “shielding effect” on RA, reducing its mechanical stability. This instability diminishes plastic energy absorption, consequently reducing impact toughness.