激光区熔定向凝固Al_2O_3/YAG/ZrO_2共晶自生复合陶瓷的显微组织与断裂韧性

Microstructure and fracture toughness of directionally solidified Al_2O_3/YAG/ZrO_2 eutectic ceramics by laser zone remelting

采用激光区熔定向凝固技术制备Al2O3/YAG/ZrO2共晶自生复合陶瓷,研究其在超高温度梯度、不同激光工艺条件下的快速凝固组织特征及其相互影响,并对其力学性能以及增韧机制进行了分析.研究结果表明:(1)激光区熔定向凝固Al2O3/YAG/ZrO2共晶由α-Al2O3、YAG以及ZrO2三相组成,不存在其他相以及相间晶团.各相均匀连续分布,耦合生长,呈网状结构,是典型的快速凝固层片状非规则共晶组织.(2)在一定的激光功率密度下,共晶间距随扫描速度的增大急剧减小,最小间距仅为0.2～0.3μm.(3)Y2O3在ZrO2中具有一定的固溶度,固溶程度不同时,ZrO2呈现不同的形貌.(4)定向凝固Al2O3/YAG/ZrO2共晶陶瓷的硬度高达18.67GPa,室温断裂韧性为8.0MPa.m1/2.第三组元ZrO2的加入、相的小尺寸效应以及裂纹分叉是韧性增强的主要原因.

Directionally solidified Al2O3/YAG/ZrO2 eutectic ceramics were prepared by laser zone remelting technique to investigate the rapid solidification microstructure characteristic under ultra-high temperature gradient and different laser processing conditions. The fracture toughness and toughen mechanism were analyzed and discussed. The results show the following. （1） The directionally solidified Al2O3/YAG/ZrO2 eutectic ceramic shows a ＇Chinese script＇ microstructure consisting of only three phases of Al2O3, YAG and ZrO2, and no other phases and colonies. The three phases distribute homogeneously and continuously, connect and finely couple each other to form an interpenetrating network, which belongs to the typical lamellar structure of a rapidly solidified irregular eutectic. （2） The eutectic spacing decreases with the increase of scanning rate under certain laser power intensity, and the smallest spacing is only about 0.2- 0.3 μm. （3） Some amount of Y2O3 dissolves in ZrO2 phase and this influences the micro-patterns of ZrO2. （4） The maximum hardness reaches 18.67 GPa and the room-temperature fracture toughness is 8.O MPa·m^1/2. Adding the third component of ZrO2, small size of phases and crack branching may contribute to the increased fracture toughness.