Study On Thermal Shock Performance Of ZrB₂-based Ultra High Temperature Cereamics Under Rapid Heating Condition

Ultra-high temperature ceramics(UHTCs)are one of the most widely used materials in the field of aerospace.Due to its excellent physical and mechanical properties,UHTCs are used as non-ablative thermal protection material in critical parts of aircraft and spacecraft.In service,UHTCs are often subjected to extremely harsh working conditions,that creates a material temperature gradient,and results a thermal shock to the material.It is extremely important to study the mechanical properties and failure mechanisms of UHTCs in this condition to improve the reliability of key structures.In this paper,aiming at the defect of traditional quenching test,the thermal shock process of rapid heating of to Zr B2-based ultra-high temperature ceramic material was studied.First of all,the method of rapid heating test was studied.The high-temperature tensile test was carried out on the material through electric heating and radiation heating.It confirmed that the electric heating test could be applied to the thermal shock test.And the elastic modulus of Zr B2 base material at high temperature was got.A thermal shock test platform based on electrical heating was built to achieve a rapid heating thermal shock test which was able to control environmental factors during the test.The effects of thermal shock temperature,heating rate,pressure,specimen size and gas environment on the thermal shock of UHTCs were investigated by means of cross-over test.The results show that the thermal shock temperature and the heating rate are the main factors affecting the test.There is a clear size effect of Zr B2-based UHTCs in thermal shock performance.Finally,a finite element software was used to model the thermal shock simulation of ultra-high temperature ceramics.The results show that the simulation of rapid heating is in good agreement with the thermal shock test under the same conditions.And the results are quite different from the simulation results of rapid cooling.It shows that the test based on quenching method can not show the actual thermal shock process,and the experimental method in this paper is an effective method to study the thermal shock performance of UHTCs.