Alloys or metallic compositions – Aluminum base – Copper containing
Reexamination Certificate
2000-12-12
2003-07-01
Wyszomierski, George (Department: 1742)
Alloys or metallic compositions
Aluminum base
Copper containing
C148S549000
Reexamination Certificate
active
06585932
ABSTRACT:
AREA OF TECHNOLOGY
The innovation belongs to the area of metallurgy of aluminum-based materials and a method of manufacturing products from such materials that can be used for recreational equipment, in various vehicles and their parts, and as an additive material for welding articles produced from aluminum-based material.
PREVIOUS LEVEL OF TECHNOLOGY
There are known aluminum-based materials that contain a matrix formed by a solid solution of certain elements, in particular, by a solid solution of copper in aluminum, and solidified particles of aluminide, including, according to (US-A N 5300157, cl. MKI(5) C22C 21/00, cl. NKI 148/437, 1994), nickel aluminides that are essentially uniformly distributed in the matrix. Such materials exhibiting a high degree of hardness and wear resistance are complex to produce and require laser technology of powder-coating materials in an inert gas atmosphere.
Also known are aluminum-based materials having a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with the magnesium content being higher than the copper content and being lower than the zinc content, and containing solidified aluminides, such as particles of nickel aluminide (SU-AI N 1061495, cl. MKI(5) C 22 C 21/10, 1992), all these particles being essentially uniformly distributed in the matrix.
Such materials exhibit high strength properties with satisfactory ductility but they are also difficult to produce, because their production requires casting by granulation technique that provides the solidification of materials at a rate no less than 1000 K/s.
The material that seems closest to the claimed material is an aluminum-based material having a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with dispersed particles of phases formed by aluminum, zinc, magnesium and copper essentially uniformly distributed in this solution. The material has a magnesium content that is higher than the copper content and lower than the zinc content. The material also contains solidified particles of nickel aluminides that constitute 3.5-11% of the total volume of the material and are essentially uniformly distributed in the matrix. (N. A. Belov et al. “The Effect of Nickel Aluminide and Magnesium Silicide on the Structure, Mechanical and Casting Properties of an Al—Zn—Mg—Cu Alloy,” Izv. Ross. Akad Nauk, Metally, No. 1, 1992, pp. 146-151).
This material combines high strength and ductility with satisfactory technological properties providing the possibility of manufacture articles by shaped castings and low pressure. However, in some cases, the durability and casting properties of such a material proved to be insufficient.
Also known is the process of making articles from an aluminum-based material by casting them from a molten mixture of aluminum, zinc, magnesium, and nickel which includes heating, holding, quenching, and aging. (N. A. Belov, V. S. Zolotorevskii, E. E. Tagiev. “The Effect of Nickel Aluminide and Magnesium Silicide on the Structure, Mechanical and Casting Properties of an Al—Zn—Mg—Cu Alloy,” Izv. Ross. Akad. Nauk, Metally, no. 1, 1992, pp. 146-151). However, this process does not allow one to obtain articles with required level and stability of mechanical properties.
SUMMARY
The main objective of the present invention is to develop an aluminum-based material exhibiting a high strength and ductility properties, namely, a tensile strength no less than 530 MPa and an elongation of no less than 2%, which provide, in combination with good technological properties, the possibility of producing items, including thin-walled articles, by means of shaped casting into metallic molds, for example under low pressure, or by liquid forging. Another objective of the invention is to develop a method for manufacturing aluminum-based articles, including thin-walled articles, having said strength and ductility properties.
In accordance with an embodiment of the present invention, an aluminum-based material having a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with uniformly distributed dispersed particles of phases formed by aluminum, zinc, magnesium and copper with the magnesium content being higher than the copper content and being lower than the zinc content, and contains solidified particles of nickel aluminide are essentially uniformly distributed in the matrix and constitute 3.5-11% of the volume of the material. The material additionally contains particles of at least one of the aluminides group consisting of chromium aluminide and zirconium aluminide, with a total content of 0.1-0.5% of the material volume, which are essentially uniformly distributed in the matrix. The matrix has a microhardness of no less than HV 170; the size of nickel aluminide particles does not exceed 3 &mgr;m, and the maximum-to-minimum size ratio of no more than 2.
The particles of chromium aluminides and zirconium aluminides are no larger than 0.05 &mgr;m. In this case, the tensile strength will be no less than 530 MPa and the elongation will be no less than 2% because the particles of chromium aluminide and/or zirconium aluminide, in combination with other strengthening phases, provide an additional strengthening of the matrix, increasing its microhardness up to a value no less than 170 HV. This value is chosen with the aim to provide the prescribed strength of the material, while the content of aluminide particles is chosen from the following considerations. If the content of the particles is lower than the minimum value, the prescribed microhardness value of the matrix is not attained; if, however, the content of the particles exceeds the maximum value, the elongation decreases below the prescribed value. The limitation on the size of the particles of nickel aluminides is set to prevent cracking and the lowering of strength and ductility of the material.
The formulated task is solved also in such a way that in order to manufacture products from aluminum-based material with tensile strength no less than 530 MPa and elongation no less than 2% by means of casting from a molten mixture of aluminum, zinc, magnesium, copper and nickel. In the process, solidification of the material is followed by heat treatment of the material, including heating, holding, quenching, and aging. According to an embodiment of the innovation, at least one of the elements from a group that includes chromium and zirconium is introduced into the molten mixture. The solidifaiton of the material is released at a rate of 2 to 90 K/s, and the heating of articles before quenching is accomplished in two steps. In the first step, the temperature is established at a level of 5-10 K lower than the temperature of nonequilibrium solidus of the material. In the second step, at a level that is higher than the nonequilibrium solidus temperature lower than the temperature of the equilibrium solidus of the material. Articles obtain, after aging, the material comprising (1) a matrix that has a microhardness no less than HV 170 and is formed by a solid solution of zinc, magnesium, and copper in aluminum and dispersed particles of phases formed by aluminum, zinc, magnesium, and copper uniformly distributed in the matrix, with a volume fraction of 3.5-11%, the maximum size no larger than 3 &mgr;m, and the maximum-to-minimum size ratio no higher than 2; and (3) particles of at least one of the aluminides selected from a group consisting of chromium aluminides and zirconium aluminides with a total volume fraction of 0.1 to 0.5% of the material volume, these particles being also uniformly distributed in the matrix.
The introduction of chromium and/or zirconium to the molten mixture of aluminum, zinc, magnesium, copper and nickel provides the formation in the material of an article of particles of chromium aluminide and/or zirconium aluminide, which increases the strength of the material. The rate of solidification indicated above makes it possible to fabricate articles by shaped casting, for example by low pressure or using liquid die forging. The temperatures prescribed for the regimes of
Axenov Andrei Anatolyevich
Belov Nikolay Alexandrovich
Zolotorevskij Vadim Semenovich
Combs Morillo Janelle
Gulliver Gregory B.
Mantraco International, Inc.
The Eclipse Group
Wyszomierski George
LandOfFree
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