半固态Al-6.5Si合金的流变特性

用半固态金属流变模型研究了Al-6.5si(质量分数，％)体系的稳态和暂态流变行为．分析表明，半固态金属的流变行为与其微结构有很强的关联，在固相体积分数一定的情况下，体系的表观粘度完全由其微结构所决定，而剪切速率和剪切时间对表观粘度的影响是通过改变体系的微结构来实现的．稳态粘度随固相体积分数的增加而增加、随剪切速率的增加而减小，这与文献中的实验结果相符合；体系的解聚过程比聚集过程快两个数量级．在各种形变条件下所出现的滞后环的大小由上升时间、静置时间、原初剪切速率、最大剪切速率等因素决定．

RHEOLOGICAL CHARACTERIZATION OF SEMISOLID Al-6.5Si ALLOYS

The rheological model developed by chen et al is applied to study the steady state and transient state behaviour of Al-6.5Si semi-solid metal (SSM) slurries. The application of the model has revealed a number of microstructural and rheological characteristics of SSM slurries. The theoretical analysis shows that there is a strong coupling between the microstructure and the steady state viscosity. It is shown that the steady state viscosity of Al-6.5Si decreases with decreasing solid fraction and increasing shear rate. This theoretical prediction is in good agreement with the experimental results in the literature. Concerning time dependent properties, but irrespective of the flow conditions, the apparent viscosity of a SSM slurry with a specified solid fraction is exclusively determined by its structure, while the effect of shear rate and shearing time is reflected by their effect on slurry structure. The deagglomeration kinetics is about two orders of magnitude faster than the agglomeration kinetics for Al-6.5Si. The model has also been successfully applied to predict the hysteresis loops under various cyclic deformation conditions.