采用旋转流变仪研究了剪切速率和不同工艺(连续冷却和重熔加热)对半固态SCN-5H₂O(摩尔分数, %)透明模型合金流变性与微观组织的耦合影响规律. 结果表明, 剪切速率的跃变升高会导致合金熔体的表观黏度呈现出暂态的剪切稠化和稳态剪切稀化现象. 而随着剪切速率的增加, 相应的组织呈现出非枝晶颗粒尺度逐渐减小, 团聚体的分布更加分散的特征, 但微观组织的形状因子随剪切速率变化不大. 半固态合金熔体在重熔加热过程中的微观组织比连续冷却过程所获得的组织, 颗粒尺度更大、形状因子略有减小, 同时, 团聚体的聚合作用更加强烈, 这也导致合金熔体在重熔加热过程中的表观黏度高于连续冷却过程所获得的数值.

The most important characteristic of semi-solid processing is that the solidification microstructure changes markedly from dendritic growth under traditional conditions to non-dendritic or globular growth, which results in apparent viscosity greatly reduction. In another hand, semi-solid slurry shows admirable fluidity compared with traditional processing slurry. With the intensive development of semi-solid meta1 processing technology, the interaction between melt flow and solidification microstructure becomes gradually one of the important fundamental research fields in materials science. In the previous work, it is very difficult to measure apparent viscosity and observe microstructure of semi-solid simultaneity using opaque metal materials. Conclusions of rheological behavior and microstructure evolution in semi-solid processing can be drawn qualitatively. Because of the metal materials not transparency and the researches on microstructure only after quenching, it is difficult to measure rheological behavior and observe dynamic microstructure evolution simultaneously. Therefore, it is also hard to grasp the coupling effect on rheology and microstructure of semi-solid alloy, which has affected the understanding and controlling accurately on solid forming process. In present paper, the coupling effect of shear rate and the processing (continuous cooling and remelted) processes on the rheology and microstructure of semi-solid SCN-5H₂O (molar fraction, %) transparent model alloys were investigated using rotating viscometer. It is found that the increase of shear rate will lead the apparent viscosity of the semi-solid alloy to present a transient shear-thickening and steady shear-thinning behavior, correspondingly, the size of non-dendritic microstructure decreases and the distribution of aggregate becomes more disperse with increasing the shear rate, while, the shape factor of the non-dendritic microstructure changes little; a larger particle size and slightly lower shape factor for non-dendritic microstructure were obtained in the semi-solid alloy slurry made by re-melted process on comparison with that by continuous cooling process, meanwhile, the aggregation of the aggregates becomes stronger, which also results in that the apparent viscosity of the semi-solid alloy slurry made by re-melted process is larger than that by continuous cooling process.