Abstract
In order to clarify the high-temperature deformation and fracture behavior of Al2O3-Y2O3 doped Si3N4, four-point bending tests were conducted at temperatures from room temperature to 1790K and at strain rates from l.Sx 10-6s-1 to 3x10-2s-1 in a nitrigen gas of 1.013x105 Pa (1 aim). As a result, the mechanical equation of state at yield stress was obtained as ε=A(σy/E)mexp(-Q/RT), where m =3.9 in the low temperature range or high strain-rale range, where m =1.7 in the high temperature range or low strain-rate range. The critical strain rate at which m changed shifted to high strain-rate side as temperature rises. It was suggested that plastic deformation of the Si3N4 was controlled by grain boundary sliding with cavity formation in the range of m=1.7, and dislocation motion and micro-crack propagation in the range of m=3.9. The activation energy for deformation Q was almost independent of strain rate when m=3.9, while Q tended to increase with decreasing strain rate when m=1.7. The relationship between deformation and fracture in Si3N4 was discussed on the basis of m value and fracture mode.
Original language | English |
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Pages (from-to) | 430-434 |
Number of pages | 5 |
Journal | Materials Transactions, JIM |
Volume | 37 |
Issue number | 3 |
DOIs | |
Publication status | Published - 1996 |
Keywords
- Cavitation, high-temperature deformation, activation energy for deformation
- Dislocation
- Grain boundary sliding
- Micro-crack
- Silicon nitride
- Strain rale
- Stress exponent
ASJC Scopus subject areas
- Engineering(all)