连续冷却条件下半固态AZ91D镁合金组织及流变特性

在自行设计的Couette型同轴双桶流变仪上对半固态AZ91D镁合金浆料的流变性能以及组织进行了研究。结果表明，连续冷却条件下，连续搅拌半固态AZ91D镁合金浆料的表面粘度随固相分数的增大先缓慢而后迅速增大。此外，冷却速率和剪切速率也都显著影响半固态AZ91D镁合金浆料的表面粘度，降低冷却速率和增大剪切速率，都将导致表观粘度下降，显微组织观察表明，降低冷却速率和增大剪切速率都有利于固相颗粒形态向非枝晶形态转变，从而导致表观粘度的降低。

MICROSTRUCTURE AND RHEOLOGICAL BEHAVIOR OF SEMI-SOLID STATE AZ91D ALLOY IN CONTINUOUSLY COOLING PROCESS

The microstructure and rheological behavior of the semi-solid state AZ91D slurry in continuously cooling and stirring process were studied by using a Couette type viscometer. The results show that the apparent viscosity of the semi-solid AZ91D magnesium alloy slowly increases originally and then sharply with increasing the solid fraction. It also has a sharp dependence on the cooling rate and the shearing rate operated on the slurry. Decreasing the cooling rate or increasing the shearing rate will lower the apparent viscosity. The analysis of the microstructure of the semi-solid state AZ91D alloy shows that this results from the solid phase shape becoming more globular due to stirring more sufficiently under lower cooling rate, or due to the larger stirring strength under higher shearing rate.