超重力下燃烧合成Al_2O_3/ZrO_2的成分、结构与性能

Composition,Microstructure and Properties of Al_2O_3/ZrO_2(4Y)Composites Prepared by Combustion Synthesis under High Gravity

通过在铝热剂中引入ZrO2(4Y)粉末,在超重力下燃烧合成制备出不同成分与结构的Al2O3/ZrO2(4Y)大体积复合陶瓷板材,并研究了复合陶瓷成分、显微结构与力学性能之间的关系。XRD、SEM与EDS分析表明,Al2O3/33ZrO2(4Y)是以取向各异且纳微米t-ZrO2纤维呈三角对称镶嵌其上的棒状共晶团为基,其周围分布着t-ZrO2微米球晶;同时,Al2O3/40ZrO2(4Y)则以t-ZrO2微米球晶为基,周围分布着不规则形状的α-Al2O3晶及少量的共晶团组织。与国外定向凝固Al2O3/ZrO2(Y2O3),Al2O3/33ZrO2(4Y)复合陶瓷比较强硬性的提高可归因于材料的高致密性、小尺寸缺陷及残余压应力增韧、相变增韧机制所导致的高断裂韧度;同时,Al2O3/40ZrO2(4Y)虽在硬度上有所下降,但弯曲强度与断裂韧度却比国外同类材料分别提高了19.0%与311.1%,故材料的强化可认为是因t-ZrO2微米球晶基体所具有的小尺寸缺陷及相变增韧与微裂纹增韧机制所诱发的高断裂韧度所致。

By introducing ZrO2(4Y)powder into the thermit,the large-scale plates of new Al_2O_3/ZrO2(4Y)composite ceramics with various component and structure were prepared by combustion synthesis under high gravity,and the correlation of component,microstructure and mechanical properties of composite ceramics were investigated by XRD(X-ray diffraction),SEM(scanning electron microscope)and EDS(energy dispersive spectrum).The results reveal that Al_2O_3/33ZrO2(4Y)is composed of random-oriented rode-shape colonies embedding by a triangular dispersion of orderly t-ZrO2 submicron fibers,surrounded by inter-colony regions consisting of nano-micrometer spherically-shape t-ZrO2 grains,meanwhile,Al_2O_3/40ZrO2(4Y)is composed of micronmeter spherically-shape t-ZrO2,surrounded by irregular-shape α-Al_2O_3 grains and a few colonies.Compared with the international directionally-solidified Al_2O_3/ZrO2(Y2O3),the increase of hardness and flexural strength of Al_2O_3/33ZrO2(4Y)are attributed to high densification,small-size defects and high fracture toughness induced by compressive residual stress toughening and transformation toughening mechanism.In addition,in despite of the moderate decrease in hardness,flexural strength and fracture toughness are increased by 19.0% and 311.1%,respectively,which is attributed to the result of small-size defect in micron-meter spherically-shaped t-ZrO2 grain matrix and high fracture toughness induced by stress-induced t-ZrO2 transformation toughening and transformation-induced micro-crack toughening mechanisms.