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<p>A new effect by deep cryogenic treatment (DCT) on enhancing twinning-induced plasticity (TWIP) in high-manganese steels is proposed. High-manganese austenitic steels derive their exceptional toughness and work-hardening capacity from deformation twinning, However, the influence of DCT on deformation twinning during subsequent room-temperature deformation has received limited attention. This work measured the lattice parameters, defect structures, and twinning kinetics of a high-Mn steel through <i>in-situ</i> cryogenic X-ray diffraction. Results revealed that DCT had induced a measurable austenite lattice contraction, reduced the microstrain by 40&#xa0;pct and the dislocation density by nearly two-thirds, and established a uniform compressive residual stress field. Microstructure observations comparing the DCT treated and as-received samples pointed to an enhanced TWIP for the DCT treated samples: twinning initiated at only 5&#xa0;pct strain, twin density was consistently higher at all deformation levels, and dense secondary and tertiary twin networks emerged, creating a refined hierarchical twin architecture. This enhanced TWIP effect strengthened twin–dislocation interactions, elevated the strain-hardening response, and increased the accumulation of geometrically necessary dislocations despite the initially lower defect content. The TWIP enhancement was attributed to a reduction of the effective stacking-fault energy and a lower barrier for Shockley partial dissociations by the DCT-generated compressive stresses. The enhanced TWIP effect produced a better toughness, with Charpy impact energy rising from 95 to 122&#xa0;J and fracture surfaces transitioning to fully ductile dimple rupture with extensive crack deflection. The findings further established DCT as a practical post-casting method for improving the durability of high-Mn steels used in severe environments.</p>

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Twinning-Assisted Toughening of High-Manganese Steels After Deep Cryogenic Treatment

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Pejman Hajipour,
  • Brianna Tian,
  • Shaofeng Sun,
  • Jack Cahn,
  • Leijun Li

摘要

A new effect by deep cryogenic treatment (DCT) on enhancing twinning-induced plasticity (TWIP) in high-manganese steels is proposed. High-manganese austenitic steels derive their exceptional toughness and work-hardening capacity from deformation twinning, However, the influence of DCT on deformation twinning during subsequent room-temperature deformation has received limited attention. This work measured the lattice parameters, defect structures, and twinning kinetics of a high-Mn steel through in-situ cryogenic X-ray diffraction. Results revealed that DCT had induced a measurable austenite lattice contraction, reduced the microstrain by 40 pct and the dislocation density by nearly two-thirds, and established a uniform compressive residual stress field. Microstructure observations comparing the DCT treated and as-received samples pointed to an enhanced TWIP for the DCT treated samples: twinning initiated at only 5 pct strain, twin density was consistently higher at all deformation levels, and dense secondary and tertiary twin networks emerged, creating a refined hierarchical twin architecture. This enhanced TWIP effect strengthened twin–dislocation interactions, elevated the strain-hardening response, and increased the accumulation of geometrically necessary dislocations despite the initially lower defect content. The TWIP enhancement was attributed to a reduction of the effective stacking-fault energy and a lower barrier for Shockley partial dissociations by the DCT-generated compressive stresses. The enhanced TWIP effect produced a better toughness, with Charpy impact energy rising from 95 to 122 J and fracture surfaces transitioning to fully ductile dimple rupture with extensive crack deflection. The findings further established DCT as a practical post-casting method for improving the durability of high-Mn steels used in severe environments.