Alloys or metallic compositions – Aluminum base – Copper containing
Patent
1997-07-09
1999-07-20
Yee, Deborah
Alloys or metallic compositions
Aluminum base
Copper containing
420532, 420534, C22C 2102, C22C 2110, C22C 2112
Patent
active
059253150
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention is directed to a cast aluminum, antifrictional alloy for bearings and general purpose applications, and a method for making the alloy.
BACKGROUND OF INVENTION
For parts operating in frictional conditions, including movable bearings, it is extremely important to minimize the frictional characteristics of the metal while maintaining sufficient wear resistance and strength. Traditionally, lead containing aluminum alloys have been utilized in frictional environments. However, due to environmental concerns, there is a trend away from the use of lead. Also, restrictions on the use of lead are becoming more common.
SUMMARY OF THE INVENTION
The present invention relates generally to an aluminum-based alloy, and a method for producing an aluminum alloy having high wear resistance and superior anti-friction characteristics. The alloy of the present invention utilizes a composition and structure, containing hard and soft constituents, which makes it possible to reach the necessary compromise between wear-resistance, strength and anti-friction characteristics.
In addition, the present invention eliminates lead without significantly reducing the tribological characteristics of the alloy.
Further, the alloy of the present invention has significantly reduced copper requirements compared to prior art alloys. Therefore, the costs of the alloy of the present invention are lower.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
In accordance with an embodiment of the invention, an aluminum-based alloy is provided having the following base composition, in weight percent:
______________________________________ Element General Preferred
______________________________________
silicon (Si): 3.0-6.0 4.0-5.5
copper (Cu): 2.0-5.0 3.0-4.5
zinc (Zn): 0.5-5.0 1.0-3.0
magnesium (Mn): 0.25-0.5 0.35-0.45
tin (Sn): 0.5-5.0 1.0-3.0
bismuth (Bi): 0.1-1.0 0.3-0.75
aluminum (Al): essentially the balance.
______________________________________
(Ni) or molybdenum (Mo), or a mixture of these, in the amount of 0.1-1.0
wt %. Traces of iron, up to 0.7 wt %, may also be present due to the
dispersion of iron from the kiln in which the alloy is created.
The unique aluminum alloy of the invention has a composition and structure containing hard and soft constituents, making it possible to achieve the necessary balance between good wear-resistance, high strength and excellent anti-friction characteristics.
The resulting alloy includes hard structural constituents formed from the above components, which increase the alloy strength, hardness, fatigue resistance, plastic deformation, and wear resistance. These hard constituents include, for example; Si, Mg.sub.2 Si, and CuAl.sub.2. The alloy also includes soft constituents, for example, Sn and Bi, which decrease the friction coefficient, decrease the tendency to scuff and bond, and increase the alloy life under impaired lubrication conditions of friction surfaces and at a reduced thickness of oil layer.
The silicon, present at the levels recited above for the alloy, also provides improved casting properties, due to the formation of an aluminum-silicon-eutectic with a melting temperature of 577.degree. C. In addition, the silicon increases alloy hardness, as stated above, increases static and fatigue strength, and increases wear resistance.
Copper, present at the levels recited above for the alloy, forms an intermetallic compound with the aluminum --CuAl.sub.2 --which has a variable solubility in a solid aluminum-based solution at different temperatures and can enter into the composition of iron-containing phases, including binary, ternary and more complex eutectics. Copper thereby promotes the increase in hardness, increases static and fatigue strength, increases fracture toughness, and increases resistance to plastic deformation and wear.
Zinc, present at the levels of an alloy of the present invention, is totally soluble in aluminum and does not form independent, separate phases, although it can be soluble in other phases. Zinc combi
REFERENCES:
patent: 4170469 (1979-10-01), Mori
patent: 4452866 (1984-06-01), Kamiya et al.
patent: 5320803 (1994-06-01), Webster
patent: 5344605 (1994-09-01), Kaji et al.
patent: 5405578 (1995-04-01), Setzer et al.
Caterpillar Inc.
Kercher Kevin M.
Yee Deborah
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