Claims
- 1. An engine valve comprising:
- grains of silicon carbide with an effective amount of aluminum for promoting beta to alpha phase transformation, the grains including a
- matrix of equi-axed grains of alpha and beta silicon carbide for optimum distribution of mechanical properties; and
- a plurality of needle-shaped grains of alpha silicon carbide comprising a single polytype of alpha silicon carbide randomly distributed within the matrix for reinforcement, the needle-shaped grains tending to arrest or deflect crack propagation.
- 2. The valve of claim 1, wherein the matrix of equi-axed grains comprises grains having an average diameter between 1-5 microns.
- 3. The valve of claim 1, wherein the plurality of needle-shaped grains comprises grains having an average length of between 20-50 microns.
- 4. The valve of claim 1, wherein the plurality of needle-shaped grains comprises grains having an average width of between 1-5 microns.
- 5. The valve of claim 1, further comprising up to 0.5 weight percent boron and traces of carbon for controlling the proportion of elongated grains distributed within the matrix of equi-axed grains.
- 6. The valve of claim 1, the valve having a density in the range of less than 3.5 grams per cubic centimeter for improved fuel economy in the engine.
- 7. The valve of claim 1, wherein the grains of silicon carbide comprise about 0.35 weight percent of aluminum.
- 8. The valve of claim 1 having an elastic modulus of up to 60 million psi, together with strengths in transverse rupture of up to 80,000 psi.
- 9. A composition of matter comprising,
- grains of silicon carbide with an effective amount of aluminum for promoting beta to alpha phase transformation, the grains including a
- matrix of equi-axed grains of alpha and beta silicon carbide for optimum distribution of mechanical properties; and
- a plurality of needle-shaped grains of alpha silicon carbide comprising a single polytype of alpha silicon carbide randomly distributed within the matrix for reinforcement, the needle-shaped grains tending to arrest or deflect crack propagation.
- 10. The composition of claim 9, wherein the grains of silicon carbide include about 0.35 weight percent of aluminum.
- 11. The composition of claim 9, wherein the matrix of equi-axed grains comprises grains having an average diameter between 1-5 microns.
- 12. The composition of claim 9, wherein the plurality of needle-shaped grains comprises grains having an average length of between 20-50 microns.
- 13. The composition of claim 9, wherein the plurality of needle-shaped grains comprises grains having an average width of between 1-5 microns.
- 14. The composition of claim 9, further comprising up to 0.5 weight percent boron and traces of carbon for controlling the proportion of needle-shaped grains distributed within the matrix of equi-axed grains.
- 15. The composition of claim 9, the valve having a density in the range of less than 3.5 grams per cubic centimeter for improved fuel economy in the engine.
- 16. The composition of claim 9, wherein the plurality of needle-shaped grains of alpha silicon carbide comprise a single polytype of alpha silicon carbide including up to 98% of the 4H polytype.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. application Ser. No. 07/842,865, filed Feb. 27, 1992, now abandoned entitled "Composition and Process for Making an Engine Valve".
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4041117 |
Prochazka |
Aug 1977 |
|
4928645 |
Berneburg |
May 1990 |
|
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
842865 |
Feb 1992 |
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