陶瓷材料高温蠕变行为研究

含有晶界玻璃相的陶瓷防热材料的高温蠕变行为主要包括晶界孔洞的成核及扩展,晶粒的滑移是控制晶界孔洞扩展的主要因素,决定了孔洞的扩展速率及扩展到完整晶界所需要的时间.建立了一个基于晶界滑移条件下单个及多个晶界孔洞扩展的模型,通过计算,给出了单个孔洞扩展的临界应力及扩展到完整晶界尺寸需要的时间,分析了在一个晶界上分别含有三晶孔洞和双晶孔洞时孔洞扩展的模式,讨论了两个孔洞在扩展过程中的相互影响,比较了前后两个孔洞在晶粒滑移条件下的扩展速率,并通过算例获得了前后两个孔洞连通与扩展同时完成的临界位置.定性及半定量的给出了晶粒滑移对蠕变陶瓷晶界孔洞扩展的影响,为计算晶界孔洞扩展到一个完整晶粒尺寸所需要时间奠定了理论基础.

Investigation on High Temperature Creep Behavior of Ceramics

High temperature creep behavior of ceramic thermal protection materials with glass phase in grain boundaries mainly contains nucleation and expansion of grain boundary cavities.Grain sliding is the major influencing factor that causes cavity expansion,which determines cavity expansion rate and the time needed for full expansion.Expansion models of single and multiple grain boundary cavities has been established,based on grain boundary sliding.The critical stress of single cavity expansion and the time needed for full expansion have been obtained numerically.Further,cavity expansion with the existence of three and two-grain cavities has been discussed and the interaction of two cavities during expansion has been elucidated.Different expansion rates have been compared and the critical position in which the two cavities connect and expand has been demonstrated in the results.The influence of grain sliding on grain boundary cavity expansion has been given qualitatively and semi-qualitatively,which provides a useful theoretical basis to the computation of the time needed for cavity expanded to a full grain size.