Process and Method For Producing Foamable Metals

Abstract

A process for producing foamable metal articles and foamed metal articles and materials. A mixture of foamable material is produced by blending at least one metal powder and one gas-producing blowing agent, then compacting the mixture into a solid form of various cross-sections and configurations. The gas-producing blowing agent comprises silicon powder and talc powder.

Description

TECHNICAL FIELD

The present invention relates to a process for producing foamable materials. More particularly, the present invention relates to mixtures of foamable metal materials produced from at least one metal powder and one gas-producing blowing agent.

BACKGROUND OF THE INVENTION

The production of foamed metal articles is known in the art. There are a variety of patents and publications concerning the production of foamed metal articles, devices and processes for producing said articles, and the metal/foaming agent mixtures used therein. The number of applications for foamed metals is high, including, but not limited to, stiffening of hollow structures, sound and vibration dampening, inhibition of energy flows, and creation of decorative elements.

Current methods of closed-cell foamed metal article production, however, typically result in cells that are irregular and coarse, often with the “windows” of the gas bubbles appearing to be fissured. In addition, prior art methods usually result in a substantial amount of unfoamed metal material at the base of the foamed metal article.

Accordingly, there is a need in the art for an improved metal/foaming agent mixture and process for the production of foamed metal articles, that results in more thorough and consistent cell formation in the foamed metal article.

SUMMARY OF THE INVENTION

This invention is directed to an improved process for producing foamable and foamed metal articles, and an improvement of the industrial properties of the foamable products and of the closed-cell foamed metal articles by comparison with the prior art.

In one exemplary embodiment, the present invention comprises a process for producing foamable metal articles, the process comprising producing a mixture of at least one metal powder and a gas-producing blowing agent, and compacting the mixture to a semi-finished foamable product or aticle, wherein the gas-producing blowing agent mixture contains some combination of silicon powder and/or talc powder (Si, [H₂Mg₃(SiO₃)₄] or [Mg₃Si₄O₁₀(OH)₂]).

In another exemplary embodiment, the present invention comprises a process of producing a foamed metal article, the process comprising subjecting the aforesaid compacted mixture and/or foamable product to conditions (e.g., elevated temperature, and/or elevated or reduced pressure) effective to foam said mixture.

In yet another exemplary embodiment, the present invention comprises the foamable metal articles produced by said processes.

Still other advantages of various embodiments will become apparent to those skilled in this art from the following description wherein there is shown and described exemplary embodiments of this invention simply for the purposes of illustration. As will be realized, the invention is capable of other different aspects and embodiments without departing from the scope of the invention. Accordingly, the advantages, drawings, and descriptions are illustrative in nature and not restrictive in nature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a process for producing foamable metal articles and foamed metal articles in accordance with an exemplary embodiment of the present invention.

FIGS. 2 and 3 show a cross-section of a foamed metal article produced in accordance with one embodiment of the present invention.

FIG. 4 shows a cross-section of a foamed metal article produced in accordance with prior art techniques.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows an exemplary embodiment of a process for producing foamable metal articles and foamed metal articles in accordance with the present invention. At least one metal powder 10 is mixed with a gas-producing blowing agent 12 containing some combination of silicon powder and/or talc powder (Si, [H₂Mg₃(SiO₃)₄] or [Mg₃Si₄O₁₀(OH)₂]). While other gas-producing blowing agents (e.g., titanium hydride, carbonates, and hydrates) have been used for producing foamable metal articles, the use of silicon powder or talc powder, or a combination of both, is not known in the art.

The combination of the metal powder 10 and the gas-producing blowing agent 12 is blended 20 and compacted 30 to form compressed foamable metal articles 40 useful for producing foamed metal articles 70. The foamable metal articles then may be exposed to elevated temperature 50, and/or elevated or reduced pressure, effective to cause the foamable metal article to foam. The material is then cooled 60, if necessary. In an alternative embodiment, the foamable metal article is placed in a mold 50 and foamed therein.

The foamed metal articles produced with the aid of the gas-producing blowing agent 12 in accordance with the present invention, especially produced auto-catalytically, have a morphology differing from that of foams obtained using prior art foaming agents (for example, titanium hydride). The foamed metal articles obtained by means of the process described herein have a very homogenous pore density distribution extending into the surface regions of the shaped foamed metal article, as seen in FIGS. 2 and 3. FIGS. 2 and 3 show an aluminum foamed product produced according to the present invention using 10% Silicon powder and 1% Talc powder as the gas-producing blowing agent mixture, and alumininum metal powder (percentages are by weight of the blended mixture).

This represents a considerable advance over foamed metal articles formed using prior art methods and prior art gas-producing blowing agents. An example of an aluminum foamed metal article produced using prior art techniques, using 1% titanium hydride as the gas-producing blowing agent, is shown in FIG. 4. The compaction and foaming conditions were identical with the process used to produce the article shown in FIGS. 2 and 3.

FIGS. 2 through 4 show a cross-section of the respective foamed metal articles, cut transversely. The foamed metal article produced using titanium hydride in accordance with the prior art shows extensive compaction (i.e., a substantial layer of unfoamed material) of the base zone 30 along the bottom of the article (see FIG. 4). The cell distribution in the foamed structure is very irregular, and the cells themselves are mainly coarse, and some have risen. This results in a somewhat fissured surface of the metal article, where large gas bubbles of this type have “blown off” on the surface.

In contrast, the foamed article produced in accordance with the present invention (shown in FIGS. 2 and 3) distinctly shows more uniform foaming. The compacted base zone in this article 26 is only approximately 0.25 mm thick, a marked improvement over the up to 10 mm thick base zone 30 shown in the prior art material (FIG. 4). In addition, the number of cells per unit volume in the foamed article produced in accordance with the present invention is distinctly greater, specifically with preference for the presence of small cells 28. Irregularity of cells is distinctly less pronounced than in the prior-art article, and the openings are finer and more uniform.

Examination of the structures of the cells in the foamed articles shown in FIGS. 2-4 reveals a peculiarity of the prior art metal foam (FIG. 4). As seen in FIG. 4, the openings in the “windows” of the gas bubbles frequently appear to be fissured 32, whereas virtually no such sites are evident in the foam of the present invention (FIGS. 2 and 3). This indicates that, at the time when the volume of the metal changed, the viscosity of the material foamed according to the prior art is less than that of the material foamed according to the invention. A possible reason for this is that titanium hydride increases the viscosity of the surrounding metal (in this case, aluminum), while the gas-producing blowing agent of the present invention has had a contrary effect.

It is possible to foam all fusible metals or metal alloys in accordance with the method described herein. In one exemplary embodiment, the metal powder particularly preferably employed for the purpose of the present invention is aluminum and its alloys. In this embodiment, the metal powder comprises essentially aluminum, and where appropriate, conventional alloying constituents including, but not limited to, magnesium, copper, and/or silicon.

Thus, it should be understood that the embodiments and examples have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive. There are several variations that will be apparent to those skilled in the art. Accordingly, it is intended that the scope of the invention be defined by the claims appended hereto.

Claims

1. A process for producing a foamed metal article, comprising the steps of: blending a mixture of at least one metal powder and one gas-producing blowing agent;and compacting the mixture to form a foamable metal article,wherein the gas-producing blowing agent comprises one or more reactive powder materials.

2. The process of claim 1, wherein the gas-producing blowing agent comprises silicon powder or talc powder or a combination thereof.

3. The process of claim 1, wherein the metal powder comprises essentially aluminum, or aluminum alloyed with one or more conventional alloying constituents.

4. The process of claim wherein the compacting is carried out by rolling, extrusion, or a combination of both.

5. The process of claim 1, wherein the compacting is carried out below the decomposition temperature of the gas-producing blowing agent mixture.

6. The process of claim 1, wherein the compacting is carried out at room temperature.

7. The process of claim 1, wherein the mixture is compacted to a density of at least 90% of the theoretical density of the metal in the metal powder.

8. The process of claim 1, wherein the mixture is compacted to a density of at least 95% of the theoretical density of the metal in the metal powder.

9. The process of claim 1, wherein the gas-producing blowing agent is from 0.1% to 12% by weight of the mixture.

10. The process of claim 1, further comprising the step of: exposing the foamable metal article to elevated temperature, and/or elevated or reduced pressure, effective to cause the foamable metal article to foam.

11. The process of claims 1, further comprising the steps of: placing said foamable metal article in a mold; andexposing the foamable metal article to elevated temperature, and/or elevated or reduced pressure, effective to cause the foamable metal article to foam.

12. A foamable metal article produced by the process of claim 1.

13. A foamed metal article produced by the process of claim 10.