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<p>The plastic instability and maintaining excellent mechanical properties of 7Mn medium manganese steel (MMnS) were restrained via the inclusion of a pre-water quenching (WQ) step before the traditional intercritical annealing (IA) treatment (at 630&#xa0;°C for 1, 2, 4 and 8&#xa0;h). The cold-rolling alloy was austenitized at 850&#xa0;°C for 0.5&#xa0;h and then water-quenched to room temperature in advance to adjust the original and final microstructures. The pre-WQ step caused the final ferrite and austenite dual-phase morphology to change from nano-equiaxed to nano-lamellar + equiaxed. The sample after traditional IA at 630&#xa0;°C for 1&#xa0;h exhibited excellent comprehensive mechanical properties, with a product of ultimate tensile strength and total elongation (UTS·TEL) of 48.9 GPa%; however, the yield point elongation (YPE) indicating typical plastic instability was as high as 17%. In contrast, the sample after WQ + IA at 630&#xa0;°C for 4&#xa0;h showed a similar UTS·TEL of 42.2 GPa%, but the plastic instability phenomena, including the formation of Lüders bands (related to YPE) and Portevin–Le Chatelier bands, were greatly restrained. This was due to the low degree of recrystallization, mixed morphology of the final microstructure, high original dislocation density in ferrite, and fine grain size resulting from pre-WQ. Additionally, the substitution of TEL with positive plasticity (PP = TEL − YPE) allowed a more accurate assessment of the comprehensive properties of MMnS. The as-prepared Lüders-band-free MMnS, with outstanding comprehensive mechanical properties, is of great significance owing to its extensive application potential in the automotive industry.</p>

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Restraining plastic instability of intercritically annealed 7Mn medium manganese steel via pre-water quenching

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Mei Zhang,
  • Wen-Hao Li,
  • Wei-Kun Wang,
  • Qing Xu,
  • Jie Zhang,
  • Qiong-Ying Cen,
  • Yang Wang,
  • Xiao-Fei Guo,
  • Han Dong

摘要

The plastic instability and maintaining excellent mechanical properties of 7Mn medium manganese steel (MMnS) were restrained via the inclusion of a pre-water quenching (WQ) step before the traditional intercritical annealing (IA) treatment (at 630 °C for 1, 2, 4 and 8 h). The cold-rolling alloy was austenitized at 850 °C for 0.5 h and then water-quenched to room temperature in advance to adjust the original and final microstructures. The pre-WQ step caused the final ferrite and austenite dual-phase morphology to change from nano-equiaxed to nano-lamellar + equiaxed. The sample after traditional IA at 630 °C for 1 h exhibited excellent comprehensive mechanical properties, with a product of ultimate tensile strength and total elongation (UTS·TEL) of 48.9 GPa%; however, the yield point elongation (YPE) indicating typical plastic instability was as high as 17%. In contrast, the sample after WQ + IA at 630 °C for 4 h showed a similar UTS·TEL of 42.2 GPa%, but the plastic instability phenomena, including the formation of Lüders bands (related to YPE) and Portevin–Le Chatelier bands, were greatly restrained. This was due to the low degree of recrystallization, mixed morphology of the final microstructure, high original dislocation density in ferrite, and fine grain size resulting from pre-WQ. Additionally, the substitution of TEL with positive plasticity (PP = TEL − YPE) allowed a more accurate assessment of the comprehensive properties of MMnS. The as-prepared Lüders-band-free MMnS, with outstanding comprehensive mechanical properties, is of great significance owing to its extensive application potential in the automotive industry.