Observations and mechanisms of fracture in polycrystalline alumina

✍ Scribed by Paul L. Gutshall; Gordon E. Gross

• Publisher: Elsevier Science
• Year: 1969
• Tongue: English
• Weight: 880 KB
• Volume: 1
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(69)90005-8

✦ Synopsis

The fracture mechanics of ~~yc~s~tine alumina have been investigated using the double cantilever beam cleavage method. The fracture resistance of ahunina was measured at temperatures up to 1500°C. The fracture resistance of ahrmina increased with increasing gram size for all temperatures studied. Electron fractography studies of the fractured surface indicate that the large grain alumina contains more transgranular fracture than the small grain material. This preponderance of transgranular fracture is shown to accompany a higher fracture resistance in the material. It is thus concluded that one mechanism of variation of strength in these materials is through variation in the relative amounts of transgran~ar and intergranular fracture. The lower softening point of SiO, causes ahunina with this material as a binder to Lose its strength at lower temperatures than does MgO bonded material. The mechanism of fracture in these ~ly~~s~lline ceramics leads to a suggested method for improved mechanical strength.