镁合金半固态浆料制备中非枝晶生长的相场法研究

摘要

The non-dendrite growth has been simulated by the phase field method in preparation of self-inoculated Mg alloy semi-solid slurry. The effects of space step on the non-dendrite growth behavior have been studied. The results showed that the crystal morphology has been determined by the structural characteristics and growing space when Mg alloy polycrystal grains were growing competitively. When the preferential growth orientation of crystal grain had larger growing space, solute enrichment degree was low in the front of the solid-liquid interface, the crystal grain grew fast and developed to dendrite trunks. However when the preferential growth orientation of crystal grain had small growing space, solute enrichment degree was high in the front of the solid-liquid interface, the tip became bald and developed to non-dendrite structure. With the increasing of space step, the trend of grain combined growth was weakened, the degree of solute enrichment and segregation decreased in the front of the solid-liquid interface.%采用相场法对镁合金自孕育半固态浆料制备中非枝晶生长过程进行模拟，研究了空间步长对非枝晶生长行为的影响。结果表明：镁合金多晶粒共同竞争生长时，晶粒形貌由晶体结构特征和生长空间共同决定。晶粒在具有较大生长空间的优先生长方向上，固液界面前沿溶质富集程度低，保持生长优势，形成主枝；晶粒在具有较小生长空间的优先生长方向上，固液界面前沿溶质富集严重，尖端变秃，形成非枝晶形貌。随着空间步长的增加，晶粒合并生长趋势减弱，固液界面前沿溶质富集和溶质偏析程度降低。