Embrittled aluminum alloys for powder manufacturing

Abstract

A powdered alloy with a chemical composition of Al.sub.xSi, where X is an amount of Si from 10 to 30 weight percent. More specifically, a powdered alloy with a chemical composition of Al.sub.xSi.sub.ySn.sub.zIn, where X is an amount of Si from 10 to 30 weight percent, Y is an amount of Sn from 0.01 to 0.50 weight percent, and Z is an amount of In from 0.005 to 0.05 weight percent.

Claims

1. A powdered alloy with a chemical composition of Al XSi YSn ZIn, where X is an amount of Si from 10 to 30 weight percent, Y is an amount of Sn from 0.01 to 0.50 weight percent, and Z is an amount of In from 0.005 to 0.05 weight percent.

Description

DRAWINGS

(1) These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims, and accompanying drawings wherein:

(2) FIG. 1 shows the Al.sub.20Si.sub.0.05Sn.sub.0.02In alloy after being crushed into smaller chunks;

(3) FIG. 2 is a plot of the alloy's open circuit potential (OCP) in 3.5% sodium chloride;

(4) FIG. 3 shows direct current potentiodynamic scans of cast Al.sub.20Si.sub.0.05Sn.sub.0.02In;

(5) FIG. 4 shows a scanning electron microscope image of ground Al.sub.20Si.sub.0.05Sn.sub.0.02In; and,

(6) FIG. 5 shows a close up scanning electron microscope image of ground ball milled Al.sub.20Si.sub.0.05Sn.sub.0.02In.

DESCRIPTION

(7) The preferred embodiments of the present invention are illustrated by way of example below and in FIGS. 1-5. A method of creating aluminum alloy powder is presented herein, the method comprising: blending and melting aluminum, silicon, tin, and indium; mixing together the melted aluminum, silicon, tin, and indium such that the following alloy is created Al.sub.20Si.sub.0.05Sn.sub.0.02In; cooling the mixed alloy; cutting the cooled alloy into smaller pieces; crushing the cut pieces; and, pulverizing and milling the crushed pieces into particles with a size of less than 200 micrometers. The alloy is a powdered alloy with a chemical composition of Al.sub.20Si.sub.0.05Sn.sub.0.02In. The preferred embodiment utilizes aluminum that is 99.99% pure so that cathodic impurities like copper (Cu) do not impede the activity of the Sn and In.

(8) The method comprises of: blending and melting aluminum of a purity from 99% to 99.999% with an embrittling element or combination of embrittling elements selected from the group consisting of silicon and germanium in the amount of 1 to 30% by weight; mixing together the melted aluminum and embrittling elements such that an alloy is created; cooling the mixed alloy; cutting the cooled alloy into smaller pieces; crushing the cut pieces; and, pulverizing and milling the crushed pieces into particles with a size of less than 200 micrometers.

(9) In one of the embodiments, 0.01% to 20% of a density reducing element selected from magnesium and lithium, or a combination thereof, may be added during the blending portion of the method. Additionally, the powdered alloy may be a chemical composition of Al-20% Si.

(10) In another embodiment, the method comprises: blending and melting aluminum of a purity from 99% to 99.999% with an embrittling element or combination of embrittling elements selected from the group consisting of silicon and germanium in the amount of 1 to 30% by weight and an activating element or combination of activating elements selected from the group consisting of indium, gallium, tin, and bismuth in the amount of 0.01% to 0.50% by weight; mixing together the melted aluminum and embrittling elements such that an alloy is created; cooling the mixed alloy; cutting the cooled alloy into smaller pieces; crushing the cut pieces; and, pulverizing and milling the crushed pieces into particles with a size of less than 200 micrometers. Optionally, 0.01% to 20% of a density reducing element selected from magnesium and lithium or a combination thereof may be added during the blending portion of the method.

(11) The subject invention is a new aluminum alloy which is both brittle (elongation <1%) and electroactive (electrical potential <0.900 volts versus saturated calomel electrode (SCE), efficiency >70%, and high current density). In one of the embodiments, the alloy is aluminum-20% silicon-0.05% tin-0.02% indium or Al.sub.20Si.sub.0.05Sn.sub.0.02In.

(12) In a preferred embodiment, this alloy can be made by melting the individual elements together in a crucible or large vessel, mixing thoroughly, and cooling in a mold. Once cooled to room temperature, the bulk aluminum can be cut into small pieces (?1 cubic centimeter), crushed or ground to approximately 1 cubic millimeter, and finally pulverized, and then milled to the final desired particle size of less than 200 micrometers. FIG. 1 shows the Al.sub.20Si.sub.0.05Sn.sub.0.02In alloy after being crushed into smaller chunks. FIGS. 2 and 3 show electrochemical data for the Al.sub.20Si.sub.0.05Sn.sub.0.02In alloy. FIG. 2 is a plot of the alloy's open circuit potential (OCP) in 3.5% sodium chloride. After 24 hours the OCP is about ?1.05 volts versus SCE, very similar to the ductile alloy used today for aluminum-rich primers (Al-5.0Zn-0.02In). The OCP is increased by about 150 millivolts compared to an alloy of Al-0.05Sn-0.02In, which is being investigated as a zinc-free alternative to the AlZnIn alloy. This increase is due to the higher electrochemical potential of the silicon (Si) added to the alloy to make it brittle. FIG. 3 is a plot of a direct current potentiodynamic scans (DCPS) of the Al.sub.20Si.sub.0.05Sn.sub.0.02In alloy. In this test, the voltage is scanned from the OCP to about 0 volts versus SCE to determine how much current the alloy supplies. The data show that the alloy provides sufficient current at anticipated operating potentials to be useful.

(13) FIGS. 4 and 5 show scanning electron microscope images of cast Al.sub.20Si.sub.0.05Sn.sub.0.02In, which has been further mechanically ground into small particles. The images show a very wide range of particle sizes from >100 microns to <1 micron with many falling into the desired range of 5-10 microns. With further optimization, the alloy or milling process can be made into a narrow particle size range with very high yield.

(14) The brittle alloy made be made using a varying amount of Si as the embrittling element or other known embrittling elements such as Ge, Ga (which can also be used as an activator), or combinations of them. For the alloys of interest to Al-rich primers, an optimum alloy is expected which balances the amount of Si with ductility and effect on electrochemical potential. Other elements may be added such as, but without limitation, magnesium (Mg) to adjust electrochemical potential and alloy density.

(15) When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles a, an, the, and said are intended to mean there are one or more of the elements. The terms comprising, including, and having are intended to be inclusive and mean that there may be additional elements other than the listed elements.

(16) Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment(s) contained herein.