Al_2O_3/Ti_2AlN复合材料的高温抗氧化行为

Oxidation Behavior of Al_2O_3/Ti_2AlN Composite at High Temperature in Air

利用综合热分析仪、扫描电镜背散射电子(BSE)和能谱分析(EDS)对Al_2O_3/Ti_2AlN复合材料在900、1000和1100℃空气中连续氧化20 h后的氧化增重及氧化层截面进行了研究。结果表明:Al2O3/Ti2AlN复合材料在空气中的氧化行为符合抛物线规律,在900、1000和1100℃,20 h氧化增重分别为2.78×10^(-2)、10.4×10^(-2)和21.9×10^(-2)kg/m^2,抛物线速率常数相应为1.08×10^(-8)、1.44×10^(-7)和6.56×10^(-7) kg^2/m^4·s,氧化激活能为274 kJ/mol。氧化层主要由TiO2和Al2O3组成的,连续的Al_2O_3次外层可以提高其抗氧化性能。氧化层结构的改变是由于氧化温度对Ti^(4+)、Al^(3+)由基体表面向外扩散和O^(2-)向内扩散的影响,以及TiO_2和Al_2O_3在不同温度下的形核生长速率导致的。对Al_2O_3/Ti_2AlN而言,控制材料与氧化气氛的界面是提高该材料抗氧化性能的关键。

The oxidation behavior in air of Al2O3/Ti2AlN composite at temperatures of 900,1000 and 1100 ℃ for 20 h were studied by oxidation mass experiment,back scanning electron imaging（BSE） and energy dispersive spectrometer（EDS）.The results show that the oxidation behavior of the composite obeys a parabolic law from 900 ℃ to 1100 ℃;its oxidation mass gain is 2.78×10^-2 at 900 ℃,10.4 ×10^-2 at 1000 ℃ and 21.9 ×10^-2 kg/m^2 at 1100 ℃,and the parabolic rate constant is 1.08×10^-8,1.44×10^-7 and 6.56×10^-7 kg^2/m^4·s,respectively.The oxide activated energy is 274 kJ/mol.The oxide layer is composed of TiO2 and Al2O3.The good oxidation resistance of Al2O3/Ti2AlN composite is attributed to the continuous outer Al2O3 layer.The structure changes of oxide layer is due to the temperature effect on the diffusion rate of Ti^4＋ and Al^3＋ ions outward and O^2- inward,as well as the nucleation and growth rate of TiO2 and Al2O3 at different temperatures.To control the interface between the matrix and oxidizing atmosphere is the key to improve the oxidation resistance of the Al2O3/Ti2AlN composite.