硼酸镁晶须增强镁基复合材料高温蠕变性能

High Temperature Creep Properties of Magnesium Matrix Composites Reinforced by Magnesium Borate Whisker

通过高温蠕变试验并对微观组织及蠕变断口形貌进行了观察,研究了硼酸镁晶须增强镁基复合材料在高温下的蠕变性能。结果表明,高温对AZ91D合金的抗蠕变性能具有很大的影响。硼酸镁晶须增强镁基复合材料在300℃﹑30MPa下的蠕变寿命达到了约24h,而基体合金只有6h,说明硼酸镁晶须对基体合金的增强作用明显。硼酸镁晶须增强镁基复合材料比基体镁合金的蠕变速率低2～3个数量级。发现了沿晶滑移和由于晶须拔出导致与基体结合的松动而产生的部分镁合金整体脱落是复合材料蠕变破坏的主要原因。

The creep properties of magnesium borate whisker reinforced magnesium matrix composites at high temperature were investigated by creep experiment. The microstructure and creep fracture morphology were also observed. The results show that the effect of high temperature on creep resistance of AZ91D alloy is obvious. The creep life of the composites at 300 ℃ under external mechanical load of 30 MPa reaches about 24 h, while the creep life of the matrix alloy is only 6 h. It indicates that the addition of Mg2B2O5 whisker strengthens AZ91D magnesium matrix. The creep rate of the composites is 2～3 orders lower than that of Mg matrix alloy. The SEM fractographs show that the fracture along the crystal plane and loosening of the matrix alloy resulting from whisker pull-out are the main failure mechanisms.