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<p>The effects of direct aging (DA) on the microstructure and mechanical properties of TiB<sub>2</sub>/AlSi7Mg alloys fabricated via laser powder bed fusion (LPBF) were systematically investigated. DA significantly improves strength while maintaining satisfactory ductility. Optimal performance is obtained through under-aging (UA) at 150°C for 4 h, resulting in a yield strength of 361 MPa, tensile strength of 503 MPa, and elongation of 9.1% in the horizontal direction. DA does not substantially alter the grain size or cellular structure but promotes the formation of nanoprecipitates within the α-Al matrix. Specifically, UA induces dot-like and needle-like Si precipitates, whereas over-aging (OA) additionally generates short rod-like β′-Mg<sub>1.8</sub>Si phases. The strengthening mechanism is attributed to the Hall–Petch effect associated with grain and cell boundaries, and the Orowan mechanism induced by nanoprecipitates. Work-hardening behavior is governed by interactions between dislocations and nanoprecipitates. The OA sample exhibits rapid saturation of work hardening due to a high initial hardening rate and dynamic recovery of dislocations, resulting in limited uniform elongation. In contrast, the UA sample demonstrates a more balanced work hardening response. These findings provide theoretical and experimental validation of DA as an effective post-processing approach aimed at enhancing the performance of LPBF Al–Si–Mg alloys in engineering applications.</p>

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Effects of direct aging on mechanical properties and microstructure of TiB2/AlSi7Mg alloy fabricated by laser powder bed fusion

  • 期刊论文

  • 发表日期：

    2025年11月24日

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  • Yirui Chang,
  • Tingting Chen,
  • Yang Li,
  • Yihao Wang,
  • Yuchi Cui,
  • Wenjun Zhao,
  • Yi Wu,
  • Mingliang Wang,
  • Haowei Wang,
  • Zhe Chen

摘要

The effects of direct aging (DA) on the microstructure and mechanical properties of TiB2/AlSi7Mg alloys fabricated via laser powder bed fusion (LPBF) were systematically investigated. DA significantly improves strength while maintaining satisfactory ductility. Optimal performance is obtained through under-aging (UA) at 150°C for 4 h, resulting in a yield strength of 361 MPa, tensile strength of 503 MPa, and elongation of 9.1% in the horizontal direction. DA does not substantially alter the grain size or cellular structure but promotes the formation of nanoprecipitates within the α-Al matrix. Specifically, UA induces dot-like and needle-like Si precipitates, whereas over-aging (OA) additionally generates short rod-like β′-Mg1.8Si phases. The strengthening mechanism is attributed to the Hall–Petch effect associated with grain and cell boundaries, and the Orowan mechanism induced by nanoprecipitates. Work-hardening behavior is governed by interactions between dislocations and nanoprecipitates. The OA sample exhibits rapid saturation of work hardening due to a high initial hardening rate and dynamic recovery of dislocations, resulting in limited uniform elongation. In contrast, the UA sample demonstrates a more balanced work hardening response. These findings provide theoretical and experimental validation of DA as an effective post-processing approach aimed at enhancing the performance of LPBF Al–Si–Mg alloys in engineering applications.