Porous metallic product and method for making same

Abstract

This invention pertains to a product and a method for making the product. The product is a lightweight solid porous metallic product containing small solid spheres having a coating of a primary alpha phase thereon disposed in a solid metal alloy eutectic matrix. The method includes the steps of mixing the hollow rigid spheres and a metal alloy, which metal alloy can be preheated to render it molten, in order to form a dispersion of the spheres distributed in the molten alloy; initially cooling the dispersion to render it semi-solid whereby the spheres are coated by a solid and the coated spheres are disposed in the semi-solid mixture of the solid and liquid; and finally cooling the sphere-containing semi-solid mixture to a temperature at which the sphere-containing semi-solid mixture becomes solid and the product is formed.

Description

FIELD OF THE INVENTION [0001] This invention pertains to the field of porous metallic objects and preparation thereof that is characterized by the use of small hollow spheres in a semi-solid mixture in a metal alloy. DESCRIPTION OF THE RELATED ART [0002] Lightweight or porous metallic materials and structures are made in honeycomb and foam core forms. Other examples are linear cellular metals and metal wire trusses. Most of these materials are made in simple shapes such as two-dimensional panels and one-dimensional bars and rods. Making these into complex three-dimensional shapes is very difficult and cost intensive. This is because of the nature of the processing routes for these materials. These materials are expensive to fabricate because they require several processing steps. Honeycomb structures are made by epoxy joining or brazing together a honeycomb arrangement made by folding thin metal ribbons. This forms the honeycomb core to which are joined face panels to make a sandwic...

AI Technical Summary

Benefits of technology

[0003] It is an object of this invention to make lightweight or porous metallic products using small, hollow ceramic or metallic particles to reduce density thereof.

[0004] It is another object of this invention to make net-shape lightweight products that do not require substantial machining.

[0005] Another object of this invention is lightweight, porous metallic products that retain greater than the expected amount of their physical properties, i.e., lower density, higher relative strength and higher relative stiffness.

[0008] Another object of this invention is a method of making a lightweight metallic product, the method being characterized by a short holding period in the semi-solid or semi-liquid state in order to stabilize the solid alpha (α) and the liquid (L1) phases.

[0010] These and other objects of this invention can be attained by preparing a lightweight, net-shape product having better than expected physical properties by mixing small ceramic and / or metallic hollow spheres with a metal alloy, such as eutectic type, heating the mixture to liquify the alloy whereby the spheres are coated with a solid primary alpha (a) phase surrounded by liquid L, phase, and solidifying the resulting mass whereby the hollow spheres have a coating of the solid primary alpha phase surrounded by the solid metal alloy of eutectic composition.

Problems solved by technology

Making these into complex three-dimensional shapes is very difficult and cost intensive.

These materials are expensive to fabricate because they require several processing steps.

Some of these materials have good stiffness but lack in other mechanical properties, such as tensile and compressive strengths.

Because of their high fabrication cost, these lightweight materials and structures have been targeted for high-end applications, such as aerospace, propulsion and ballistic protection.

Many of these materials are made abroad and availability thereof is severely restricted.

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