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<p>Microstructural control is crucial in laser powder bed fusion (LPBF) technique. The columnar-to-equiaxed transition is an effective approach to reduce anisotropy and improve mechanical properties of additively manufactured materials. Recent studies have shown that grain refinement can be induced through heterogeneous nucleation ahead of the epitaxially growing solid–liquid (S/L) interface. This paper investigated the solidification process of a metal matrix composite (FeMnAlC-TiB) produced by LPBF, which resulted in a texture-free nano-equiaxed <i>δ-Fe</i> matrix, reinforced by nanoprecipitates and an <i>M</i><sub><i>2</i></sub><i>B-type</i> network structure. The analysis of electron backscatter diffraction (EBSD), transmission electron microscopy-automatic crystal orientation and phase mapping (TEM-ASTAR), and three-dimensional atom probe (3DAP) indicated that boron (B) segregation plays a major role in terms of microstructure refinement by generating a thermal undercooling zone ahead of the S/L interface. As a result of the microstructural refinement and the presence of reinforced particles, the LPBF-processed material exhibited hardness 150% higher than the base steel and achieved remarkable levels of strength as compared with the as-cast counterparts.</p> Graphical abstract <p></p>

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Segregation-induced microstructural refinement in a FeMnAlC-TiB metal matrix composite by laser powder bed fusion

  • 期刊论文

  • 发表日期：

    2025年5月6日

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  • André L. Vidilli,
  • Leonardo F. Gomes,
  • Adriel P. Oliveira,
  • Mainak Saha,
  • Taisuke Sasaki,
  • Lucas B. Otani,
  • Ilya Okulov,
  • Claudemiro Bolfarini

摘要

Microstructural control is crucial in laser powder bed fusion (LPBF) technique. The columnar-to-equiaxed transition is an effective approach to reduce anisotropy and improve mechanical properties of additively manufactured materials. Recent studies have shown that grain refinement can be induced through heterogeneous nucleation ahead of the epitaxially growing solid–liquid (S/L) interface. This paper investigated the solidification process of a metal matrix composite (FeMnAlC-TiB) produced by LPBF, which resulted in a texture-free nano-equiaxed δ-Fe matrix, reinforced by nanoprecipitates and an M2B-type network structure. The analysis of electron backscatter diffraction (EBSD), transmission electron microscopy-automatic crystal orientation and phase mapping (TEM-ASTAR), and three-dimensional atom probe (3DAP) indicated that boron (B) segregation plays a major role in terms of microstructure refinement by generating a thermal undercooling zone ahead of the S/L interface. As a result of the microstructural refinement and the presence of reinforced particles, the LPBF-processed material exhibited hardness 150% higher than the base steel and achieved remarkable levels of strength as compared with the as-cast counterparts.

Graphical abstract