The influence of microstructure on the mechanical behavior of silicon nitride ceramics

Conference · Thu Dec 31 04:00:00 EST 1992

OSTI ID:10164104

Becher, P F; Lin, H T; Hwang, S L ^[1]; Hoffmann, M J ^[2]; Chen, I-Wei ^[3]

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1. Oak Ridge National Lab., TN (United States)
2. Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany). Pulvermetallurgisches Lab.
3. Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science

Elongated Si nitride grains produced during densification in a liquid phase can increase the fracture toughness, but this depends on the activation of intergranular rather than transgranular fracture. Bridging in the crack wake by elongated grains and pullout of some of these grains suggest that the crack wake mechanisms that contribute to toughening of whisker-reinforced ceramics can also operate in Si nitrides containing elongated grains. With diameters of the larger elongated grains approaching 9 {mu}m, strengths > 800 MPa have been achieved along with Weibull moduli, but clustering of these larger elongated grains must be avoided. Fatigue of these toughened Si nitrides is influenced by silicate grain boundary phases. Design of toughened Si nitrides must consider effects of silicate phase composition and content on fatigue and creep. 8 figs, 18 refs.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States); German Federal Ministry of Science and Technology (Germany)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10164104
• Report Number(s): CONF-921101--131; ON: DE93015363; CNN: Grant AF0SR-91-0094; Grant 03M2012
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203
CRACK PROPAGATION
CRACKS
CREEP
FATIGUE
FRACTURE PROPERTIES
GRAIN SIZE
MECHANICAL PROPERTIES
SILICON NITRIDES