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<p>The columnar-to-equiaxed transition (CET) significantly influences materials' mechanical properties, corrosion resistance and processability. Understanding and controlling it remain a central challenge in metal casting and solidification. In this study, using a Bridgman-type furnace, directional solidification experiments of grain refined and non-refined Al-3.5 wt.%Si and Al-10 wt.%Cu hypoeutectic alloys were conducted to systematically investigate the CET processes and their mechanisms. Detailed statistical analyses of the dendritic and grain structures, as well as the compositional distributions, were also carried out. The results showed that CET occurred in the refined alloys, while in the non-refined alloys, columnar dendrites continued to grow. Under the interaction of gravity-induced thermosolutal convection, Si was enriched toward the center and upper regions of the samples, while Cu was enriched toward the center and lower regions. In the refined alloy samples, the axial macrosegregation of Si and Cu became more severe because of gravity-induced floating or sedimentation of equiaxed nuclei. Although the overall trends of dendrite arm spacing and grain size were consistent across all samples, the rates and extents of these changes varied significantly with alloy composition and solidification morphology under the coupled effects of gravity and process factors.</p>

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Effects of Gravity and Process Factors on Dendrite Growth, Columnar-to-Equiaxed Transition, and Compositional Segregation in Directional Solidification of Al-3.5 wt.% Si and Al-10 wt.% Cu Alloys

  • 期刊论文

  • 发表日期：

    2025年11月13日

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  • Guiyuan Zhang,
  • Xinghong Luo,
  • Yang Li,
  • Shi Liu

摘要

The columnar-to-equiaxed transition (CET) significantly influences materials' mechanical properties, corrosion resistance and processability. Understanding and controlling it remain a central challenge in metal casting and solidification. In this study, using a Bridgman-type furnace, directional solidification experiments of grain refined and non-refined Al-3.5 wt.%Si and Al-10 wt.%Cu hypoeutectic alloys were conducted to systematically investigate the CET processes and their mechanisms. Detailed statistical analyses of the dendritic and grain structures, as well as the compositional distributions, were also carried out. The results showed that CET occurred in the refined alloys, while in the non-refined alloys, columnar dendrites continued to grow. Under the interaction of gravity-induced thermosolutal convection, Si was enriched toward the center and upper regions of the samples, while Cu was enriched toward the center and lower regions. In the refined alloy samples, the axial macrosegregation of Si and Cu became more severe because of gravity-induced floating or sedimentation of equiaxed nuclei. Although the overall trends of dendrite arm spacing and grain size were consistent across all samples, the rates and extents of these changes varied significantly with alloy composition and solidification morphology under the coupled effects of gravity and process factors.