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<p>Laser powder bed fusion (LPBF) of pure tungsten is inherently challenged by severe thermal gradients and its high ductile-to-brittle transition temperature (DBTT), which promote crack formation during rapid solidification. In this work, the focus is shifted from empirical parameter optimization to mechanism-driven regulation of thermal history. By combining numerical simulations with multiscale microstructural characterization, a critical processing window (210&#xa0;W/450&#xa0;mm/s) was identified, achieving a high relative density of 99.02% with negligible cracking. The cyclic thermal history inherent to LPBF was found to drive thermally activated dislocation rearrangement, resulting in a stable nanoscale sub-grain boundary network (20–50&#xa0;nm) through polygonization. Based on these observations, a thermal-history-mediated multiscale crack-suppression framework is proposed. Regulation of thermal history stabilizes melt-pool dynamics and eliminates macroscopic stress concentrators, while tortuous grain-boundary networks promote crack deflection at the mesoscale and nanoscale sub-grain structures facilitate localized stress relaxation. Consequently, the fabricated tungsten exhibits superior mechanical performance, with a hardness of 487 HV and a compressive strength of 1094&#xa0;MPa. These findings identify thermal history as the governing variable linking process parameters, microstructural evolution, and fracture behavior, providing mechanistic guidance for designing crack-resistant LPBF processing windows for refractory metals.</p>

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Thermal-history-mediated multiscale crack suppression in laser powder bed fusion of pure tungsten

  • 期刊论文

  • 发表日期：

    2026年5月22日

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  • Xiao-Qiang Zhang,
  • Run-Song Li,
  • Bi-Wei Lu,
  • Run-Ze Hao,
  • Xiao-Yong Zhu,
  • Jia-Qin Liu,
  • Yu-Cheng Wu

摘要

Laser powder bed fusion (LPBF) of pure tungsten is inherently challenged by severe thermal gradients and its high ductile-to-brittle transition temperature (DBTT), which promote crack formation during rapid solidification. In this work, the focus is shifted from empirical parameter optimization to mechanism-driven regulation of thermal history. By combining numerical simulations with multiscale microstructural characterization, a critical processing window (210 W/450 mm/s) was identified, achieving a high relative density of 99.02% with negligible cracking. The cyclic thermal history inherent to LPBF was found to drive thermally activated dislocation rearrangement, resulting in a stable nanoscale sub-grain boundary network (20–50 nm) through polygonization. Based on these observations, a thermal-history-mediated multiscale crack-suppression framework is proposed. Regulation of thermal history stabilizes melt-pool dynamics and eliminates macroscopic stress concentrators, while tortuous grain-boundary networks promote crack deflection at the mesoscale and nanoscale sub-grain structures facilitate localized stress relaxation. Consequently, the fabricated tungsten exhibits superior mechanical performance, with a hardness of 487 HV and a compressive strength of 1094 MPa. These findings identify thermal history as the governing variable linking process parameters, microstructural evolution, and fracture behavior, providing mechanistic guidance for designing crack-resistant LPBF processing windows for refractory metals.