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<p>The ability of additive manufacturing processes to control solidification at a microscopic scale is of particular interest in the development of components with topology-optimised microstructures. Leveraging laser powder bed fusion (L-PBF), we present a new methodology to develop site-specific “microstructure architectures” consisting of dissimilar phases. By controlling the laser focal offset in a bespoke L-PBF machine, we tailor the melt pool shape and control the volume of material that undergoes re-heating during each melting event. Using a high-carbon low alloy steel as a case study material, we demonstrate control over the formation of tempered and un-tempered phases at the resolution of the laser spot size (~10<sup>2</sup> µm) and in 3-D throughout the build. Although the tensile strength of the steel is limited by the presence of keyhole porosity and solidification cracking, our strategy showcases the opportunity to vary hardness site-specifically and by up to 2.4 GPa, opening the path to producing alloys with novel microstructure and property complexity.</p>

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Localised control of phase formation in a high-carbon low alloy steel by laser powder bed fusion

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年3月30日

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  • Karl Peter Davidson,
  • Tan Phuc Le,
  • Linh Lan Nguyen,
  • Jude Emil Pascua Fronda,
  • Ruiliang Liu,
  • Tzee Luai Meng,
  • Yee Yan Tay,
  • Matteo Seita

摘要

The ability of additive manufacturing processes to control solidification at a microscopic scale is of particular interest in the development of components with topology-optimised microstructures. Leveraging laser powder bed fusion (L-PBF), we present a new methodology to develop site-specific “microstructure architectures” consisting of dissimilar phases. By controlling the laser focal offset in a bespoke L-PBF machine, we tailor the melt pool shape and control the volume of material that undergoes re-heating during each melting event. Using a high-carbon low alloy steel as a case study material, we demonstrate control over the formation of tempered and un-tempered phases at the resolution of the laser spot size (~102 µm) and in 3-D throughout the build. Although the tensile strength of the steel is limited by the presence of keyhole porosity and solidification cracking, our strategy showcases the opportunity to vary hardness site-specifically and by up to 2.4 GPa, opening the path to producing alloys with novel microstructure and property complexity.