搅拌法制备漂珠增强铝基复合材料的熔体分层与控制

MELT DELAMINATION AND CONTROL IN CENOSPHERE FLY ASH REINFORCED COMPOSITES PREPARED BY STIR CASTING

采用液态搅拌法制备漂珠增强铝基复合材料过程中,当颗粒含量较低时,熔体容易分层。为了了解颗粒在铝熔体中的分布情况,对试样的不同位置进行扫描电镜分析。结果表明,在试样的底部有明显的纯铝层,而漂珠在上部的铝熔体中分布均匀。漂珠向熔体上部移动的速度主要取决于漂珠颗粒与铝熔体的密度差、颗粒直径、颗粒体积分数及铝熔体粘度。原料确定后,只能通过增加铝熔体的粘度或减少浇铸过程的时间来减少纯铝层的产生。因此,可以采用下浇铸式方法和快速冷却装置,使颗粒来不及向上运动而被凝固在铝熔体中,形成漂珠在铝熔体中均匀分布的复合材料。

When the cenosphere fly ash content is lower, the melt is easily delaminated during preparing the cenosphere fly ash reinforced aluminium composites by stir casting technology. In order to realize the distribution of cenosphere fly ash in the aluminium melt, the different parts of the sample were analyzed by SEM. The results indicate that there is a pure aluminium layer in the bottom of the sample, but the cenosphere fly ash distributes evenly in the top of the aluminium melt. The velocity of the cenosphere fly ash moving to the top of the melt was determined by the difference of density between cenosphere fly ash and aluminium, diameter and volume fraction of particles, as well as viscosity of the aluminium melt. To reduce the pure aluminium layer, the viscosity of the aluminium melt should be increased or the time of casting process should be reduced for the certain material. The down casting method and quick chiller are employed, so that the cenosphere fly ash has no enough time to move upward and solidify in the aluminium melt, and the cenosphere fly ash distributes evenly in the aluminium melt.