The strength of Al{sub 2}O{sub 3}/SiC nanocomposites after grinding and annealing

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(98)00068-8· OSTI ID:644304

Wu, H Z; Lawrence, C W; Roberts, S G; Derby, B ^[1]

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1. Univ. of Oxford (United Kingdom). Dept. of Materials

Alumina matrix nanocomposites containing about 5 vol.% SiC of <100 nm mean particle size show a substantial increase in strength after machining and annealing. The final strength is controlled by the annealing process and achieves the same level after a coarse machining using 150-grit diamond as is achieved using a complex lapping and polishing sequence. In all cases the final anneal leads to an increase in strength. The nanocomposite retains a significantly higher residual surface-compression stress level than an equivalent grain size alumina after machining. A remnant stress, of about 20% of the initial level, is retained even after 10 h annealing at 1,250 C. Hertzian indentation and measurements of Rayleigh wave velocity show that the nanocomposite surfaces contain defects of smaller size and density than are found in equivalent aluminas. Annealing appears to result in healing of existing surface defects thus increasing the nanocomposite strength while leaving its toughness unchanged. The crack-healing mechanism is associated with a chemical process on the nanocomposite surface which has been tentatively identified as an oxidation leading to amorphous mullite formation.

• OSTI ID: 644304
• Report Number(s): CONF-9704224--
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 11 Vol. 46; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
ANNEALING
COMPOSITE MATERIALS
DEFECTS
GRINDING
RESIDUAL STRESSES
SILICON CARBIDES
ULTIMATE STRENGTH