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<p>The synergistic effects of grain refinement and low temperature on the deformation mechanisms of Cr–Mn–N austenitic stainless steels (ASSs) were systematically investigated. Fine-grained (FG) structures were fabricated via cold rolling (60 pct reduction) and annealing (1000&#xa0;°C, 60&#xa0;s), achieving an average grain size of 1.7&#xa0;μm, while coarse-grained (CG) counterparts retained 10.4&#xa0;μm. Tensile tests at room temperature (RT, 25&#xa0;°C) revealed that grain refinement significantly enhanced yield strength (FG: 684&#xa0;MPa vs. CG: 392&#xa0;MPa at RT) but reduced elongation (FG: 45 pct vs. CG: 60 pct) due to restricted dislocation motion. Notably, lowering the temperature to − 78&#xa0;°C dramatically increased yield strength (FG: 1237&#xa0;MPa, CG: 511&#xa0;MPa) while maintaining ductility (FG: 54 pct, CG: 56 pct). This exceptional strength-ductility synergy in FG structures (static toughness: 81,830&#xa0;MPa·pct) stemmed from reduced stacking fault energy (SFE: 22.6 → 17.5&#xa0;mJ/m<sup>2</sup>), which suppressed deformation twins (DTs) and accelerated geometrically necessary dislocation (GND) accumulation. The surge in GND density (FG: 11.07 × 10<sup>14</sup>/m<sup>2</sup>) promoted early nucleation of deformation-induced martensite (DIM, 95 vol pct), triggering a transformation-induced plasticity (TRIP) effect. At RT, DIM formation was limited (FG: 6 vol pct) due to high SFE and grain-boundary-induced austenite stability. In contrast, low-temperature deformation shifted the dominant mechanism from dislocation slip and DTs to dislocation slip and TRIP-driven DIM, enabling uniform strain distribution and delayed necking. These findings highlighted the critical role of temperature-modulated SFE in optimizing deformation pathways, providing a novel strategy to enhance the low-temperature performance of cost-effective Cr–Mn–N ASSs for polar applications.</p>

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Revealing the Synergistic Effects of Grain Refinement and Low Temperature on the Deformation Mechanisms of Cr–Mn–N Austenitic Stainless Steel

  • 期刊论文

  • 发表日期：

    2025年4月30日

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  • Zhi Wang,
  • Chengyang Hu,
  • Hangyu Dong,
  • Xiangliang Wan,
  • Xiangtao Deng,
  • Rui Ke,
  • Guangqiang Li,
  • Kaiming Wu

摘要

The synergistic effects of grain refinement and low temperature on the deformation mechanisms of Cr–Mn–N austenitic stainless steels (ASSs) were systematically investigated. Fine-grained (FG) structures were fabricated via cold rolling (60 pct reduction) and annealing (1000 °C, 60 s), achieving an average grain size of 1.7 μm, while coarse-grained (CG) counterparts retained 10.4 μm. Tensile tests at room temperature (RT, 25 °C) revealed that grain refinement significantly enhanced yield strength (FG: 684 MPa vs. CG: 392 MPa at RT) but reduced elongation (FG: 45 pct vs. CG: 60 pct) due to restricted dislocation motion. Notably, lowering the temperature to − 78 °C dramatically increased yield strength (FG: 1237 MPa, CG: 511 MPa) while maintaining ductility (FG: 54 pct, CG: 56 pct). This exceptional strength-ductility synergy in FG structures (static toughness: 81,830 MPa·pct) stemmed from reduced stacking fault energy (SFE: 22.6 → 17.5 mJ/m2), which suppressed deformation twins (DTs) and accelerated geometrically necessary dislocation (GND) accumulation. The surge in GND density (FG: 11.07 × 1014/m2) promoted early nucleation of deformation-induced martensite (DIM, 95 vol pct), triggering a transformation-induced plasticity (TRIP) effect. At RT, DIM formation was limited (FG: 6 vol pct) due to high SFE and grain-boundary-induced austenite stability. In contrast, low-temperature deformation shifted the dominant mechanism from dislocation slip and DTs to dislocation slip and TRIP-driven DIM, enabling uniform strain distribution and delayed necking. These findings highlighted the critical role of temperature-modulated SFE in optimizing deformation pathways, providing a novel strategy to enhance the low-temperature performance of cost-effective Cr–Mn–N ASSs for polar applications.