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<p>5.5Ni cryogenic steel was developed through a microalloying design. A lamellar treatment, added between traditional quenching and tempering (QT) processes, is referred to as QLT process. By adjusting the reversed transformation austenite/ferrite phase content in the lamellar microstructure, a fibrous texture was achieved in 5.5Ni cryogenic steel. This adjustment promotes the redistribution of C, Mn, and Ni elements within the microstructure during the subsequent tempering process. This reduces the resistance to deformation of the microstructure by external forces and produces a higher number of high-angle grain boundaries. As the lamellarization temperature decreases, the formation of fiber structures reduces the tendency for martensite variants to form in the microstructure, encouraging the formation of reversed transformation austenite. The self-regulation of martensite variant stress, the blocking of cracks by high-angle grain boundaries, and the deflection effect of reversed transformation austenite on cracks enhance the impact toughness of 5.5Ni cryogenic steel. Additionally, during uniaxial tensile testing, when shear stress is parallel to the habit plane of the slip system, the material exhibits easier sliding and greater plastic deformation. Furthermore, the special textures (Brass, Goss, E-type and copper) in the microstructure promote uniform plastic deformation. Therefore, when shear stress aligns with both the slip plane and the special texture, the plasticity of the material is maximized. Using this process, 5.5Ni cryogenic steel with a yield strength of 658&#xa0;MPa, elongation of 23.90%, and impact energy of 178&#xa0;J at 77&#xa0;K was successfully produced.</p>

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Influence of martensite variant and special texture on toughness and plasticity of 5.5Ni cryogenic steel

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Zhong-Lin Wu,
  • Guang-Ming Cao,
  • Yang Sun,
  • Yi-Fan Ji,
  • Wei-Na Zhang,
  • Cheng-Gang Li,
  • Peng-Jie Wang,
  • Biao Deng,
  • Zhao-Xia Liu,
  • Zhen-Yu Liu

摘要

5.5Ni cryogenic steel was developed through a microalloying design. A lamellar treatment, added between traditional quenching and tempering (QT) processes, is referred to as QLT process. By adjusting the reversed transformation austenite/ferrite phase content in the lamellar microstructure, a fibrous texture was achieved in 5.5Ni cryogenic steel. This adjustment promotes the redistribution of C, Mn, and Ni elements within the microstructure during the subsequent tempering process. This reduces the resistance to deformation of the microstructure by external forces and produces a higher number of high-angle grain boundaries. As the lamellarization temperature decreases, the formation of fiber structures reduces the tendency for martensite variants to form in the microstructure, encouraging the formation of reversed transformation austenite. The self-regulation of martensite variant stress, the blocking of cracks by high-angle grain boundaries, and the deflection effect of reversed transformation austenite on cracks enhance the impact toughness of 5.5Ni cryogenic steel. Additionally, during uniaxial tensile testing, when shear stress is parallel to the habit plane of the slip system, the material exhibits easier sliding and greater plastic deformation. Furthermore, the special textures (Brass, Goss, E-type and copper) in the microstructure promote uniform plastic deformation. Therefore, when shear stress aligns with both the slip plane and the special texture, the plasticity of the material is maximized. Using this process, 5.5Ni cryogenic steel with a yield strength of 658 MPa, elongation of 23.90%, and impact energy of 178 J at 77 K was successfully produced.