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<p>TiB<sub>2</sub>-modified Fe<sub>40</sub>Cr<sub>20</sub>Co<sub>20</sub>Ni<sub>20</sub> (at%) high-entropy alloy (HEA) samples were fabricated using a conventional laser powder bed fusion (LPBF) method at four batches of volumetric energy densities (VEDs). The as-printed specimens exhibited visible metallurgical defects, including pores and microcracks, accompanied by cellular structures with elemental segregation (predominantly Cr enrichment) and brittle σ phase precipitation at cell boundaries. Partial melting of TiB<sub>2</sub> reinforcement particles during processing resulted in the formation of tiny TiO<sub>2</sub> particles in the alloy matrix. Microstructural evolution analysis revealed that increasing VED induced three primary modifications, i.e., progressive reduction of printing defects, gradual homogenization, and continuity of element segregation in cell walls, and suppressed σ phase formation but increased dispersive nanoscale TiB<sub>2</sub>/TiO<sub>2</sub> particles. The overall mechanical properties improve with increasing VED, namely the yield strength (YS) increases from 640 to 700&#xa0;MPa, the ultimate tensile strength (UTS) increases from 920 to 960&#xa0;MPa, and the elongation (El) improves from 3.4% to 6.6%. The best performing sample produced at a VED of ~ 156.2&#xa0;J&#xa0;mm<sup>−3</sup> showed a 66.7% increase in YS and 104.2% increase in UTS compared to the TiB<sub>2</sub>-free counterpart (YS ~ 420&#xa0;MPa, UTS ~ 470&#xa0;MPa). Moreover, theoretical calculations indicate that the strengthening mechanism of TiB<sub>2</sub>-modified Fe<sub>40</sub>Cr<sub>20</sub>Co<sub>20</sub>Ni<sub>20</sub> HEA is mainly a synergistic effect of extra dislocation hardening and Orowan-type particle strengthening. This work confirms the feasibility of the TiB<sub>2</sub> reinforcing strategy in some soft LPBF-produced HEAs and gives new insights into developing high-performance alloys for structural applications.</p> Graphical abstract <p></p>

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Correlating the microstructures and mechanical behaviors in a TiB2-modified Fe40Cr20Co20Ni20 high-entropy alloy fabricated by laser powder bed fusion

  • 期刊论文

  • 发表日期：

    2025年9月1日

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  • Hong-Liang Hu,
  • De-Cheng Jiang,
  • Wei-Ying Huang,
  • Peng-Da Niu,
  • Ke-Fu Gan

摘要

TiB2-modified Fe40Cr20Co20Ni20 (at%) high-entropy alloy (HEA) samples were fabricated using a conventional laser powder bed fusion (LPBF) method at four batches of volumetric energy densities (VEDs). The as-printed specimens exhibited visible metallurgical defects, including pores and microcracks, accompanied by cellular structures with elemental segregation (predominantly Cr enrichment) and brittle σ phase precipitation at cell boundaries. Partial melting of TiB2 reinforcement particles during processing resulted in the formation of tiny TiO2 particles in the alloy matrix. Microstructural evolution analysis revealed that increasing VED induced three primary modifications, i.e., progressive reduction of printing defects, gradual homogenization, and continuity of element segregation in cell walls, and suppressed σ phase formation but increased dispersive nanoscale TiB2/TiO2 particles. The overall mechanical properties improve with increasing VED, namely the yield strength (YS) increases from 640 to 700 MPa, the ultimate tensile strength (UTS) increases from 920 to 960 MPa, and the elongation (El) improves from 3.4% to 6.6%. The best performing sample produced at a VED of ~ 156.2 J mm−3 showed a 66.7% increase in YS and 104.2% increase in UTS compared to the TiB2-free counterpart (YS ~ 420 MPa, UTS ~ 470 MPa). Moreover, theoretical calculations indicate that the strengthening mechanism of TiB2-modified Fe40Cr20Co20Ni20 HEA is mainly a synergistic effect of extra dislocation hardening and Orowan-type particle strengthening. This work confirms the feasibility of the TiB2 reinforcing strategy in some soft LPBF-produced HEAs and gives new insights into developing high-performance alloys for structural applications.

Graphical abstract