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<p>In laser-based powder bed fusion (PBF-LB/M) additive manufacturing (AM), the layer-by-layer fabrication of free-form thin walls is subjected to rapid thermal cycling, inducing significant temperature gradients. These gradients result in nonuniform thermal expansion and contraction, leading to the accumulation of residual stresses that, when exceeding critical thresholds, trigger structural instability such as buckling and complete build failure. This study investigates the buckling mechanisms of free-form thin walls in relation to residual stress evolution during the PBF-LB/M process. Dense, sub-100&#xa0;µm free-form Ti6Al4V thin-walls were successfully printed, achieving a minimum feature thickness of approximately 75&#xa0;µm to evaluate the buckling mechanism. Experimental results reveal that thin walls buckle at critical heights due to a substantial reduction in bending stiffness. Notably, the thin-wall aspect ratio, defined as the ratio of critical buckling height (H<sub>cr</sub>) to wall thickness (t), remained consistent at approximately 31.5 for sub-150&#xa0;µm thin walls across varying process conditions. This demonstrates a fundamental geometric constraint governing thin-wall stability in PBF-LB/M. Additionally, we establish an empirical correlation demonstrating that H<sub>cr</sub> is a direct function of peak residual stress (Y) and wall thickness (t). Furthermore, we identify three distinct stages of residual stress evolution that either lead to catastrophic build failure or induce wall branching. This study provides new insights into the manufacturability of ultra-thin walls using conventional laser-based PBF, elucidating the key factors that limit their maximum achievable build height.</p>

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Critical geometrical constraints and buckling phenomena in Ti6Al4V ultra-thin walls printed by laser-based powder bed fusion

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月29日

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  • Arif Hussain,
  • Junghoon Lee,
  • Jae Hee Kim,
  • Hae Ju Park,
  • Young Sam Kwon,
  • Dongsik Kim

摘要

In laser-based powder bed fusion (PBF-LB/M) additive manufacturing (AM), the layer-by-layer fabrication of free-form thin walls is subjected to rapid thermal cycling, inducing significant temperature gradients. These gradients result in nonuniform thermal expansion and contraction, leading to the accumulation of residual stresses that, when exceeding critical thresholds, trigger structural instability such as buckling and complete build failure. This study investigates the buckling mechanisms of free-form thin walls in relation to residual stress evolution during the PBF-LB/M process. Dense, sub-100 µm free-form Ti6Al4V thin-walls were successfully printed, achieving a minimum feature thickness of approximately 75 µm to evaluate the buckling mechanism. Experimental results reveal that thin walls buckle at critical heights due to a substantial reduction in bending stiffness. Notably, the thin-wall aspect ratio, defined as the ratio of critical buckling height (Hcr) to wall thickness (t), remained consistent at approximately 31.5 for sub-150 µm thin walls across varying process conditions. This demonstrates a fundamental geometric constraint governing thin-wall stability in PBF-LB/M. Additionally, we establish an empirical correlation demonstrating that Hcr is a direct function of peak residual stress (Y) and wall thickness (t). Furthermore, we identify three distinct stages of residual stress evolution that either lead to catastrophic build failure or induce wall branching. This study provides new insights into the manufacturability of ultra-thin walls using conventional laser-based PBF, elucidating the key factors that limit their maximum achievable build height.