US1945297A - Aluminum alloy - Google Patents

Description

Patented Jan. 30, 1934 UNITED STATES ALUMINUM ALLOY Roland Sternen-Rainer, Heilbronn, Germany, assignor to American Lurgi Corporation, New York, N. Y., a corporation of New York No Drawing. Application November 24, 1930., Serial No. 497,956, and in Germany December 7 Claims.

My present invention comprises an improved cast, forged, drawn or rolled aluminum alloy with additions of magnesium and silicon andof a metal of the group consisting of manganese, nickel. cobalt, chromium, iron and titanium, or a metal of the group antimony, cadmium and bismuth, or a combination of metals of these two groups. It is the object of my invention to improve the physical properties of the cast, forged, drawnor rolled alloy.

Heretofore aluminum alloys containing copper and magnesium. have been improved by heat treatment. The improvement has been ascribed to the tendency of certain components, particularly copper-aluminum or copper-magnesiumaluminum particles, to be thrown out of solution from the. aluminum during the aging after the heat treatment. 7

If the alloy is free from copper another element must be added which.-with the aluminum and magnesium, is able to form mixed crystals in order to render possible a technically valuable improvement of the physical properties by heat treatment. For example, zinc is used as such an element. Silicon is also known as an addition element, but it has only been possible to get a noticeable improvement of the properties of such an alloy by so-called artificial aging, that is storing at a temperature over 100 C. On the other hand, it is known that some addition elements are valueless ,for magnesium-containing aluminum alloys, as they combine with the magnesium to form a compound insoluble in aluminum and so hinder the precipitation of particles from solution. Antimony is, for instance, such an element. It should be noted however that antimony is a very valuable component for an aluminum alloy in so far as the production of a non-corroding alloy is concerned. In such cases, antimony forms non-corroding films.

I have now discovered that some combinations containing aluminum alloys with additions of other elements both show the good qualities of a non-corrosive alloy and can be improved by heat treatment. Such combinations are primarily aluminum alloys with at least 0.1% to 6% 'Inagnesium, 0.6% to 6% silicon and at least 0.2% to 10% of a metal of the group consisting of manganese, nickel, chromium, cobalt, iron and titanium. It should here be noted that the alloy does not contain any substantial amount of copper other than as a possible impurity and that, nevertheless, it can be improved by a schedule of heat treatment hereinafter described in detail.

' The improvement by heat treatment is due particularly to the simultaneous presence of magnesium and silicon, but it is further strengthened by the presence of one or more metals of the group hereinbefore defined.

If, for instance, an alloy which has an approximate composition of 2% magnesium; 1 1% manganese, 96.6% aluminum (the aluminum containing the normal impurities of, say, 0.3% to 0.4% iron and silicon) issand cast, it has a tensile strength of about 17 kg. per sq. mm. and an elongation of 3 to 5%. If this alloy is heated to a temperature of 570 C. and quenched, no improvement of the tensile strength is effected by aging at normal temperature. Forged, drawn or rolled material, of the foregoing composition, has a tensile strength of about 22 kg. per sq. mm. and, in a state of plasticity, anelongation of 22 24%, and cannot be improved either by artificial or natural aging. On the contrary, if, in accordance with my invention, the alloy has a composition which varies from the above by the addition of 0.6% silicon, so that the total silicon content amounts to 0.9%, and further such an alloy is heated some hours at a temperature of 570 C., quenched and aged at normal, that is to say, room temperature for several days, then the tensilestrength is increased to 23 kg. per sq. mm. for east alloys and to about 34 kg. per sq. mm. for rolled alloys. The elongation however is not altered.

To show, on the other hand, the importance of the manganese content, it may be stated that a forged aluminum, alloy, containing only 0.75% silicon and 0.5% magnesium, which was heated at a temperature of about 560 C., quenched and aged at room temperature for '7 days, had a tensile strength of 22 kg./sq. mm. and an elongation of 30%. If about 1% manganese is further added and the alloy treated in the same manner by heating to 560 C., quenching and aging at room temperature for '7 days, it has a. tensile strength of about 32 kg. per sq. mm. and an elongation of about 24%.

It will be seen from these examples that neither the addition of magnesium and silicon alone,.nor the addition of magnesium and manganese alone, to aluminum, eifects any considerable improvement of the aluminum alloys by heating, quenching, and aging at room temperature, but only the simultaneous presence of magnesium, silicon and manganese.

Other metals, such as nickel, cobalt, chromium, iron or titanium, can naturally be added instead of .manganese in proportions of 0.2% to 10%, either alone or combined, without depart Instead of a metal of the group h ereinbeforev defined, or in addition thereto, a metal of the group consisting of antimony, cadmium and bismuth can be used in order to further improve the properties of the alloy, especially as regards resistance to corrosion. The limit for the addition of antimony, cadmium and bismuth is 5%, because the antimony forms an insoluble combination with the magnesium." Care should be taken that there is always more magnesium present than corresponds to the stoicheometric amount required for the combination withantimony, in order to form magnesiumsilicide, which dissolves in the solid state in the aluminum.

When an alloy with 2% magnesium, 1.4% manganese, 0.2% antimony, 0.9% silicon, remainder aluminum, is sand cast, it has a tensile strength of about 18 kg. per sq. mm. and an elongation of about 3 to 5%. If this alloy is heated at about 570 C. for about three hours, quenched and aged at room temperature for at least 4 days, .the tensile strength amounts to 24 kg. per sq. mm. A further improvement is ob-' tained if the forged, drawn or rolled material, rather than the cast material, is subjected to the heat treatment. In this case, an alloy, comprising about 2% magnesium, 1.4% manganese, 0.2% antimony, 0.9% silicon, remainder aluminum, after heat treatment has a tensile strength of about 35 kg. per sq. mm. and an elongation of about 22 to 24%.

In this specification and in the claims, .the terms heating and aging are intended to cover not only the specific temperatures enumerated herein but also the known variations of these temperatures which are permissible under various conditions known to those skilled in the arts. For example, it is known that heating of an alloy canbe carried out at a lower temperature if the length of the heating step is correspondingly increased.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. An aluminum alloy substantially devoid or copper and composed of from 0.8% to 6.0% of magnesium, from 0.6% to 6.0% of silicon, from 0.2% to 5% of at least one metal of the group consisting of manganese, nickel, cobalt, chromium, titanium and iron, and aluminum the remainder, said alloy being further characterized by increased tensile strength with simultaneous maintenance of' high resistance to corrosion by means of a heat treatment consisting of heat treating the alloy at a temperature closely below the solidification point, quenching and finally aging at room temperature for a period of several days.

2. An aluminum alloy substantially devoid of copper and composed of from 0.2% to 6.0% of magnesium, from 0.6% to 6.0% of silicon, from 0.2% to 5% of a metal of the group consisting of manganese, nickel, cobalt, chromium, titanium and iron, from 0.05% to 5.0% of a metal of the group consisting of antimony, cadmium and bismuth, and aluminum the remainder, said alloy being further characterized by increased tensile strength with simultaneous maintenance of high resistance to corrosion by means of a heat treatment consisting of heat treating the alloy at a temperature closely below the solidfication point, quenching and finally aging at room temperature for a period of several days.

3. An aluminum alloy improved in tensile strength by a treatment consisting of heating to incandescence, quenching and aging at room temperature for a period of several days, said alloy being characterized by the following constitution: magnesium 2%; manganese 1.4%; silicon 0.9%; antimony 0.2%; with aluminum the remainder.

4. An aluminum alloy improved in tensile strength by a treatment consisting of heating to incandescence, quenching and aging at room temperature for a period of several days, said alloy being characterized by the following constitution: magnesium 0.5%; manganese 1.0%; 0.75%; with aluminum the remainder.

- 5. An aluminum alloy improved in tensile strength by a treatment consisting of heating to incandescence, quenching and aging at room temperature for a period of several days, said alloy being characterized by the following constitution: magnesium 2.0%; manganese-1.4%; silicon 0.9%;

with aluminum the remainder.

6. Method of improving the tensile strength and other physical properties of an aluminummagnesium-silicon alloy substantially devoid of silicon copper and containing magnesium within the range of from 0.2% to. 6.0%.and silicon within the range of from 0.6% to 6.0%, with aluminum the remainder, without destroying the capacity of that alloy to be improved by a heat treatment which involves heat treating the alloy at a temperature closely below the solidification point, quenching and finally aging at room temperature for a period of several days, which method consists in alloying therewith from 0.2% to 5% of a metal of the arbitrary group consisting of manganese, nickel, cobalt, chromium, titanium and iron.

ganese, nickel, cobalt, chromium, titanium and iron, and from 0.05% to 5.0% of a metal of the arbitrary group consisting of antimony, cadmium and bismuth.

- ROLAND STERNER-RAINER.

'7. Method of improving the tensile strength and l