Al_2O_3–ZrO_2复相陶瓷的低温力学性能和热学性能

采用无压烧结法制备Al2O3–15%（质量分数）ZrO2（简称ZTA）复相陶瓷,研究了ZTA复相陶瓷在293～77K的力学性能以及300～5K的热学性能,分析了ZTA复相陶瓷在不同温度断裂时断面上ZrO2发生的相变量和相变区宽度。结果表明：ZTA复相陶瓷的抗弯强度、断裂韧性和Vickers硬度均随温度下降而逐渐提高;77K时抗弯强度、断裂韧性和Vickers硬度比293K时分别提高了10.8%、19.7%和10.4%;ZTA复相陶瓷的热导率随温度下降先增大,在97K时达到最大值,然后随温度下降而降低。低温环境增强了ZTA复相陶瓷中应力诱导t-ZrO2→m-ZrO2的相变增韧效应,提高了ZTA复相陶瓷的低温力学性能。ZTA复相陶瓷具有良好的低温力学性能和较小的低温热导率,是一种有广阔应用前景的低温结构陶瓷材料。

Mechanical and Thermal Properties of Al2O3-ZrO2 Composite Ceramics at Cryogenic Temperatures

The alumina with zirconia of 15% (in mass)(ZTA) composite ceramics were prepared by a pressureless sintering process. The mechanical properties of ZTA composite ceramics in a temperature range of 293 to 77 K and the thermal properties in a temperature range of 300 to 5 K were investigated. The phase transformation volume and zone width of ZrO 2 in the fracture surface of ZTA composite ceramics at various temperatures were also analyzed. The results reveal that the bending strength, fracture toughness and Vickers hardness of ZTA composite ceramics increase linearly with decreasing temperature, and they are increased by 10.8%, 19.7% and 10.4% at 77 K, respectively, compared to those at 293 K. The thermal conductivity of ZTA composite ceramics at 97 K firstly increased to a maximum value, and then decreased with decreasing the temperature. The improvement of mechanical properties of ZTA composite ceramics at cryogenic temperatures was due to the enhanced stress-induced tetragonal to monoclinic phase transformation toughening. The thermal conductivity of ZTA composite ceramics at cryogenic temperatures was rather low, which could meet the demand of cryogenic engineering. The ZTA composite ceramics could be one of the most promising materials in cryogenic structural applications.