相场法研究Al影响Mg-3wt%Y-1wt%Zn合金非等温凝固枝晶生长和溶质偏析

Phase-Field Study of Al Addition Effects on Dendritic Growth and Solute Segregation During Non-Isothermal Solidification of Mg-3wt%Y-1wt%Zn Alloy

摘要:

利用多元定量相场建模，研究了添加Al对Mg-3wt%Y-1wt%Zn合金凝固行为的影响，重点分析了α-Mg枝晶的生长动力学、溶质偏析及二次枝晶臂间距的调控机制。结果表明，Al的加入显著抑制α-Mg枝晶的生长速率，降低了固相分数增长速度。同时，Al添加有效缓解了Zn的微观偏析，使Zn的偏析度大幅降低，但对Y的偏析影响较小。此外，Al通过降低液相线温度、抑制溶质扩散及减小固/液界面能，促进了二次枝晶臂的细化。成分过冷理论分析表明，高Al含量加剧溶质富集，导致更大的过冷度，从而影响枝晶形核与生长。本研究有助于深入理解如何优化Mg-Y-Zn-Al合金的凝固组织、改善力学性能及耐蚀性能。

Abstract:

A multi-component quantitative phase-field model was developed to investigate the influence of the Al addition on the solidification behavior of Mg-3wt%Y-1wt%Zn alloy. The study focused on the growth kinetics, solute segregation, and controlling mechanism of secondary dendrite arm spacing (SDAS) of α-Mg dendrites. The results show that Al addition significantly suppresses the growth rate of α-Mg dendrites and reduces the growth rate of solid fraction. Moreover, Al effectively mitigates Zn microsegregation, substantially decreasing the segregation ratio, while having only a minor effect on Y segregation. Furthermore, Al promotes SDAS refinement by lowering the liquidus temperature, inhibiting solute diffusion, and reducing solid/liquid interfacial energy. Constitutional undercooling analysis indicates that higher Al content enhances solute accumulation, leading to increased undercooling, thereby altering dendritic nucleation and growth. This study provides valuable insights for optimizing the solidification microstructure and enhancing the mechanical properties and corrosion resistance of Mg-Y-Zn-Al alloys.