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AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsJonathan A. Lee, Po-Shou Chen
Estimating the term…
A cast article from an aluminum alloy has improved mechanical properties at elevated temperatures. The cast article has the following composition in weight percent: Silicon 6.0-25.0, Copper 5.0-8.0, Iron 0.05-1.2, Magnesium 0.5-1.5, Nickel 0.05-0.9, Manganese 0.05-1.2, Titanium 0.05-1.2, Zirconium 0.05-1.2, Vanadium 0.05-1.2, Zinc 0.05-0.9, Strontium 0.001-0.1, Phosphorus 0.001-0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10-25, and the copper-to-magnesium ratio is 4-15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a L12 crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix containing up to about 60% by volume of a secondary filler material.
A cast article from an aluminum alloy, which has improved mechanical properties at elevated temperatures, the cast article having the following composition in weight percent:
A process for making a cast article from an aluminum alloy, which article has improved mechanical properties at elevated temperatures, the process comprising:
A metal matrix composite comprising an aluminum alloy having the following composition in weight percent:
An aluminum alloy having the following composition in weight percent:
Dependencies are inferred from the claim text.
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With silicon as the next major constituent: modified aluminium-silicon alloys
Non-ferrous alloys containing at least 5% by weight but less than 50%
Light metals: aluminium
Of aluminium or alloys based thereon: of alloys with silicon as the next major constituent
Term end not estimated
1. Field of The Invention
This invention relates generally to aluminum-silicon (Al—Si) alloys. It relates particularly to a high strength Al—Si based alloy suitable for high temperature applications for cast components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and brake rotors.
2. Description of the Related Art
FIG. 1 is a diagram illustrating a coherent particle that has similar lattice parameters and crystal structure relationship with the surrounding aluminum matrix atoms.
FIG. 2 is a diagram illustrating a non-coherent particle having no crystal structural relationship with the surrounding aluminum matrix atoms. Such an alloy has little or no practical application at elevated temperatures.
FIG. 3 is an electron micrograph showing the size and shape of the alloy θ′ and S′ coherent phases for prior art alloys as observed at room temperature.
The present invention includes detailed compositional, microstructure and processing aspects through conventional casting processes. The Al—Si alloy of the present invention is marked by an ability to perform in cast form, which is suitable for elevated temperature applications. It is comprised of the following elements, in weight percent: 1 Silicon 6.0-25.0 Copper 5.0-8.0 Iron 0.05-1.2 Magnesium 0.5-1.5 Nickel 0.05-0.9 Manganese 0.05-1.2 Titanium 0.05-1.2 Zirconium 0.05-1.2 Vanadium 0.05-1.2 Zinc 0.05-0.9 Strontium 0.001-0.1 Phosphorus 0.001-0.1 Aluminum Balance
Silicon gives the alloy a high elastic modulus and low thermal coefficient of expansion. The addition of silicon is essential in order to improve the fluidity of the molten aluminum to enhance the castability of the Al—Si alloy according to the present invention. At high silicon levels, the alloy exhibits excellent surface hardness and wear resistance properties.
Copper co-exists with magnesium and forms a solid solution in the aluminum matrix to give the alloy age-hardening properties, thereby improving the high temperature strength. Copper also forms the θ′ phase compound (Al2Cu), and is the most potent strengthening element in this new alloy. The enhanced high strength at high temperatures is affected if the copper wt % level is not adhered to. Moreover, the alloy strength can only be maximized effectively by the simultaneous formation for both of the θ′ (Al2Cu) and S′ (Al2CuMg) metallic compounds, using proper addition of magnesium into the alloy relative to the elements of copper and silicon. Experimentally, it is found that an alloy with a significantly higher level of magnesium will form mostly S′ phase with insufficient amount of θ′ phase. On the other hand, an alloy with a lower level of magnesium contains mostly θ′ phase with insufficient amount of S′ phase.