ムライトセラミックスのクリープ

概要

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Creep in mullite ceramics containing 71 , 74 and 78 wt% Al_2O_3 made from coprecipitated powder has been studied between 1350° to 1500℃. Microstructure of 71 wt% Al_2O_3 mullite was characterized by rod-like and equiaxed grains (average grain size : 2.13 μm) , that of 74 wt% Al_2O_3 mullite, by equiaxed grains (grain; size : 5.44 μm), and that of 78 wt% Al_2O_3 mullite, by equiaxed mullite grains (grain size : 2.11 μm) and Al_2O_3 particles of 1.31 μm in grain boundaries. Creep rate in 74 wt% Al_2O_3 mullite was the lowest and that of 71 wt% Al_2O_3 was the highest. That of 78 wt% Al_2O_3 mullite located in between. Activation energies for creep were 138, 168 and 119 kcal/mol for 71, 74 and 78 wt% Al_2O_3 mullite, respectively. Vertical offsets from grain sliding out of the specimen surface were observed after creep test. The number of grains indicating the vertical offsets increased and cavities evolved with increasing creep time or applied stress. A slight grain growth was observed for 71 and 78 wt% Al_2O_3 mullites after creep tests. On the other hand, grain growth was not recognized for 74 wt% Al_2O_3 mullite. It was proposed that the creep mechanism in mullite ceramics is grain boundary sliding accompanied by diffusion.
社団法人日本セラミックス協会の論文
1989-06-01