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<p>Laser powder bed fusion (LPBF) provides a new venue to tune microstructures due to the unique melt pool dynamics. In this study, an interlayer retention printing strategy was developed in LPBF of Type 316L austenitic stainless steel. The solidification cells typically decorated by element segregation faded as the laser power increased. The formation of the solidification cell-faded zone was remarkably coincident with the occurrence of multiple twinning, which promotes equiaxed and refined grains with an average size of 14&#xa0;μm and a high fraction ~ 55% of Σ3<sup>n</sup> (n = 1, 2, 3…) grain boundaries. It was assumed that the interlayer retention printing strategy at a high laser power level enhanced dynamic recrystallization (DRX) via in-situ annealing, during which element segregation was alleviated and multiple twinning was introduced. As a result, an excellent strength-ductility trade-off was achieved for the samples fabricated at a high volumetric energy density of 162&#xa0;J/mm<sup>3</sup> and interlayer retention of 5&#xa0;min. This work demonstrated that microstructures of 316L stainless steel is in-situ refined via multiple twinning, which significantly improves the mechanical properties.</p>

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In-situ grain refinement induced by multiple twinning in 316L austenitic stainless steel fabricated by laser powder-bed fusion

  • 期刊论文

  • 发表日期：

    2025年10月19日

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  • L. C. Cao,
  • C. C. Li,
  • F. L. Shen,
  • T. J. Ma,
  • L. T. Pan,
  • W. H. Xin,
  • Z. Lyu,
  • X. Y. Fang,
  • L. J. Li

摘要

Laser powder bed fusion (LPBF) provides a new venue to tune microstructures due to the unique melt pool dynamics. In this study, an interlayer retention printing strategy was developed in LPBF of Type 316L austenitic stainless steel. The solidification cells typically decorated by element segregation faded as the laser power increased. The formation of the solidification cell-faded zone was remarkably coincident with the occurrence of multiple twinning, which promotes equiaxed and refined grains with an average size of 14 μm and a high fraction ~ 55% of Σ3n (n = 1, 2, 3…) grain boundaries. It was assumed that the interlayer retention printing strategy at a high laser power level enhanced dynamic recrystallization (DRX) via in-situ annealing, during which element segregation was alleviated and multiple twinning was introduced. As a result, an excellent strength-ductility trade-off was achieved for the samples fabricated at a high volumetric energy density of 162 J/mm3 and interlayer retention of 5 min. This work demonstrated that microstructures of 316L stainless steel is in-situ refined via multiple twinning, which significantly improves the mechanical properties.