激光悬浮区熔Al_2O_3基共晶自生复合材料微观组织与力学性能  

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF Al_2O_3BASIC EUTECTIC IN SITU COMPOSITES DIRECTIONALLY SOLIDIFIED BY LASER FLOATING ZONE REMELTING

作　　者：贾晓娇[1] 张军[1] 苏海军[1] 宋衎[1] 刘林[1] 傅恒志[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072

出　　处：《金属学报》2012年第12期1479-1486,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51002122和51272211;陕西省自然科学基金项目2010JQ6005;航空科学基金项目2010ZF53064资助~~

摘　　要：采用激光悬浮区熔定向凝固方法制备了高致密度Al_2O_3/YAG/ZrO_2共晶自生复合陶瓷材料,研究多元复相陶瓷在高温度梯度、不同生长条件下的凝固组织形态演化规律,定量表征凝固速率与氧化物陶瓷共晶间距的关系,在此基础上,考察其力学性能并分析凝固组织与断裂韧性的关系.研究结果表明:激光悬浮区熔Al_2O_3/YAG/ZrO_2三元自生复合材料呈现与热流方向平行、定向性良好的非规则层片共晶形貌,共晶组织随凝固速率的增大而快速细化,凝固速率为200μm/s时,最小层片间距达到0.46μm.平均层片间距λav与凝固速率V之间符合关系:λ_(av)V^(0.5)=12.4μm^(1.5)·s^(-0.5),且明显小于同等凝固速率条件下Al_2O_3/YAG二元共晶的平均层片间距.Al_2O_3/YAG/ZrO_2三元共晶平均硬度为(19.0±1.0)GPa,室温断裂韧性为(3.31±0.2)MPa·m^(1/2).与二元共晶相比,裂纹捕获、偏转以及共晶相热胀系数失配是三元共晶室温断裂韧性提高的主要原因.Directionally solidified oxide eutectic in situ composites have been attracting increasing interest in recent years for use as the next generation of ultra-high-temperature structural materials because of their excellent high-temperature strength, oxidation and creep resistance, as well as outstanding microstructural stability. AI203/YAG/ZrO2 ternary eutectic in situ composites with high density are prepared by laser floating zone remelting technique. The microstructure evolution of AI203/YAG/ZrO2 ternary eutectic under high temperature gradient and different growth rates is investigated. The relationship between solidification rate and eutectic spacing for the ternary oxide eutectic is quantificationally characterized. On this basis, the mechanical properties and relationship between microstructure and fracture toughness are analysed. The results show that the directionally solidified AI203/YAG/ZrO2 ternary eutectic in situ composite belongs to typical irregular lamellar entectic structure. The microstructure is rapidly refined with the increase of the solidification rate V.The minimal eutectic spacing observed is as fine as 0.46 μm when the solidification rate is 200 μm/s. The relationship between the average eutectic spacing （tav） and V is determined to be AavV0.5= 12.4 μml5.s-0.5. Moreover, the ternary eutectic lamellar spacing is much smaller than the binary one at the same solidification condition. The average hardness and room-temperature fracture toughness of the ternary eutectic are （19.04±1.0） GPa and （3.314±0.2） MPa.m1/2, respectively. As compared with the binary eutectic, the crack arrest, deflection and mismatch of thermal expansion coefficient of eutectic phases are the predominant toughening mechanisms of ternary eutectic composite.

关 键 词：激光悬浮区熔 定向凝固 三元共晶 自生复合材料 凝固组织 断裂韧性 

分 类 号：TG142[一般工业技术—材料科学与工程]