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<p>To address the synergy commonly observed in intercritical annealed medium-Mn steels, tempering treatment was applied to optimize the mechanical properties of medium-Mn steel. The effects of tempering temperature (150-700&#xa0;℃) on the microstructure and mechanical properties were systematically investigated. The results demonstrate that the as-forged steel primarily consists of three phases: lath martensite, retained austenite (RA), and δ-ferrite. Notably, the martensite laths exhibit a cross-hatched arrangement, forming an ordered topological configuration through their interaction with RA films at lath boundaries and δ-ferrite along grain boundaries. During low-temperature tempering (&lt; 300&#xa0;℃), carbon redistribution occurs, leading to the gradual blurring of both martensite lath boundaries and prior austenite grain boundaries, resulting in a microstructure dominated by tempered martensite. As the tempering temperature increases, martensite progressively decomposes along with the coarsening of granular carbides, transforming ultimately into tempered sorbite at 600&#xa0;℃. Tempering significantly enhances the steel’s plasticity with a notable increase in elongation. The optimal strength-ductility match was achieved at 200&#xa0;°C tempering for 1&#xa0;h, attributed to modulation of transformation-induced plasticity (TRIP) effect via carbon partitioning and effective relief of residual stress relief. Correspondingly, the fracture morphology changes from brittle (before tempering) to ductile fracture (after tempering).</p>

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Effect of Tempering Temperature on the Microstructure and Properties of Hot-Forged Medium-Mn Steel

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Kun Ma,
  • Yi Xiong,
  • Yong Li,
  • Yi-yi Wang,
  • Hua-fei Li,
  • Xiao-qin Zha,
  • Feng-zhang Ren,
  • Shu-bo Wang

摘要

To address the synergy commonly observed in intercritical annealed medium-Mn steels, tempering treatment was applied to optimize the mechanical properties of medium-Mn steel. The effects of tempering temperature (150-700 ℃) on the microstructure and mechanical properties were systematically investigated. The results demonstrate that the as-forged steel primarily consists of three phases: lath martensite, retained austenite (RA), and δ-ferrite. Notably, the martensite laths exhibit a cross-hatched arrangement, forming an ordered topological configuration through their interaction with RA films at lath boundaries and δ-ferrite along grain boundaries. During low-temperature tempering (< 300 ℃), carbon redistribution occurs, leading to the gradual blurring of both martensite lath boundaries and prior austenite grain boundaries, resulting in a microstructure dominated by tempered martensite. As the tempering temperature increases, martensite progressively decomposes along with the coarsening of granular carbides, transforming ultimately into tempered sorbite at 600 ℃. Tempering significantly enhances the steel’s plasticity with a notable increase in elongation. The optimal strength-ductility match was achieved at 200 °C tempering for 1 h, attributed to modulation of transformation-induced plasticity (TRIP) effect via carbon partitioning and effective relief of residual stress relief. Correspondingly, the fracture morphology changes from brittle (before tempering) to ductile fracture (after tempering).