NIST Standard Reference Database 30
Last Update to Data Content: 2002
"Fracture and Intermediate Temperature Instability in Yttria-Doped Hot-Pressed Silicon Nitrides," R.K. Govila, American Ceramic Society Bulletin, Vol. 65 [9], pp. 1287-1292 (1986), published by American Ceramic Society.Language: English
Billets were 150 mm x 150 mm x 25 mm. WC balls used in ball-milling led to WSi2 contamination. Specimens were machined to 32 mm x 6 mm x 3 mm with tensile faces perpendicular to the hot-pressing direction; faces were ground lengthwise using 320 grit diamond wheels; and edges were chamfered lengthwise. Sintering aids were 7-8% Y2O3 plus 1-2% Al2O3.
The measurement was made by four-point bend method using a self-aligning fixture, 1/4-point loading, Instron test machine (Model 1125), and crosshead speed = 0.5 mm/min. Specimens were heated at test temperature for 30 min to 45 min before testing in air.
| Amount of Element ( formula units ) |
Element ( no unit ) |
|---|---|
| 3 | Si |
| 4 | N |
| Sintering Aid Mass Fraction ( % ) |
Sintering Aid ( no unit ) |
|---|---|
| 7.5 ± 0.5 | Y2O3 |
| 1.5 ± 0.5 | Al2O3 |
| Mass Fraction of Impurity ( % ) |
Impurity ( no unit ) |
|---|---|
| 0.50 | Al |
| 0.05 | Ca |
| 0.75 | Fe |
| 0.10 | Mg |
| 3.00 | W |
| Temperature ( °C ) |
Flexural Strength ( MPa ) |
|---|---|
| 20 | 851 ± 85 |
| 400 | 807 ± 65 |
| 500 | 799 ± 74 |
| 600 | 719 ± 143 |
| 700 | 636 ± 157 |
| 800 | 653 ± 140 |
| 1000 | 656 ± 104 |
The authors suggested that failure strength is independent of temperature up to 500 °C.
| Temperature ( °C ) |
Weibull Modulus ( no unit ) |
|---|---|
| 20 | 12 |
| 400 | 15 |
| 500 | 13 |
| 600 | 5.8 |
| 700 | 4.6 |
| 800 | 5.4 |
| 1000 | 7.4 |
| Temperature ( °C ) |
Weibull Strength ( MPa ) |
|---|---|
| 20 | 886 |
| 400 | 834 |
| 500 | 828 |
| 600 | 770 |
| 700 | 690 |
| 800 | 703 |
| 1000 | 692 |