Aluminum-based alloy

Abstract

The incorporation of calcium and at least one member selected from the group consisting of vanadium and scandium into an aluminum lithium alloy containing: lithium, copper, magnesium, zirconium, beryllium, titanium, nickel, manganese, gallium, zinc, and sodium provides an aluminum lithium alloy that: 1) exhibits improved ductility; 2) exhibits improved processability resulting in the capability to obtain higher yields of semi-finished products; 3) provides the ability to fabricate thin sheets, thin walled sections and forgings, all while preserving the inherent strength and operating characteristics of such alloys when applied to semi-finished products and parts thereof demanded by structural applications in these fields.

Description

FIELD OF THE INVENTION[0001]The present invention relates to aluminum lithium alloys and more particularly to an aluminum-copper-magnesium-lithium alloy that overcomes the shortcomings of prior such alloys.BACKGROUND OF THE INVENTION[0002]It is well known that aluminum lithium alloys possess a unique combination of mechanical properties including; low density, high modulus of elasticity, and high strength. These properties contribute to the use of these alloys as structural materials in aerospace applications that result in a number of improvements in aircraft / aerospace vehicle performance including: reduction in vehicle weight, fuel economy and increased load capacity.[0003]However, aluminum lithium alloys as a group exhibit at least one major disadvantage, low ductility under conditions at or near their maximum strength. (N. I. Friedlander, K. V. Christos. A. L. Berezina, N. I. Kolbe, Aluminum Lithium Alloys, Structure and Properties, Kiev: Nauk. Dumka, 1992, page 177).[0004]Among...

AI Technical Summary

Benefits of technology

[0014]It is a further object of the present invention to provide an aluminum lithium alloy that: 1) exhibits improved ductility; 2) exhibits improved processability resulting in the capability to obtain higher yields of semi-finished products; 3) provides the ability to fabricate thin sheets, thin walled sections and forgings, all while preserving the inherent strength and operating characteristics of such alloys when applied to semi-finished products and parts thereof demanded by structural applications in these fields.SUMMARY OF THE INVENTION

Problems solved by technology

However, aluminum lithium alloys as a group exhibit at least one major disadvantage, low ductility under conditions at or near their maximum strength.

The disadvantages of these alloys are their limited processability, the high manufacturing costs associated therewith that are dictated by the labor intensiveness of such activities, low yields of satisfactory product obtained in the fabrication of semi-finished products and parts and the difficulties encountered when fabricating thin sheets, thin walled sections and forgings therefrom.

These disadvantages are due, at least in part, to the fact that the relatively high concentrations of copper in these alloys contribute to hot brittleness and negatively affect the ductility thereof.

This leads to cracking, high rejection levels in folds and non-flatness in finishing operations that include flattening and stretching to form finished or semi-finished products.

The disadvantages of this alloy include, high cost, their limited processability, the high manufacturing costs associated therewith that are dictated by the labor intensiveness of such activities, low yields of satisfactory product obtained in the fabrication of semi-finished products and parts and the difficulties encountered when fabricating thin sheets, thin walled sections and forgings therefrom.

The major cause of the aforementioned disadvantages is the relatively elevated concentration of lithium in this alloy which results in the formation of strengthening phases during forming operations.

The formation of these strengthening phases reduces the alloy's ductility during casting and shaping.

This, in turn, results n increased cracking, higher rejections based on the presence of folds and non-flatness in finishing operations that include flattening and stretching during the fabrication of semi-finished or finished products.

Among the disadvantages of this alloy are its limited processability, the high manufacturing costs associated therewith that are dictated by the labor intensiveness of such activities, low yields of satisfactory product obtained in the fabrication of semi-finished products and parts and the difficulties encountered when fabricating thin sheets, thin walled sections and forgings therefrom.

These disadvantages are due, at least in part, to the fact that the relatively high concentrations of copper in these alloys contribute to hot brittleness and negatively affect the ductility thereof.

This leads to cracking, high rejection levels in folds and non-flatness in finishing operations that include flattening and stretching to form finished or semi-finished products.

Additionally, the relatively high levels of sodium and gallium lead to a considerable increase in the hot brittleness of the alloy with a consequent reduction in the ductility thereof.

This complicates considerably obtaining acceptable ingots and the fabrication of various semi-finished products by shaping.

This also inhibits the production of quality claddings for rolled or semi-finished products as a result of the formation of significant areas of non-welded cladding on the surface.