US1718642A - Light-metal alloy - Google Patents

Description

Patented June 1929.

UNITED STATES JOHN A. GANN, OF MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COM- PANY, 0F MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN.

LIGHT-METAL ALLOY.

No lirawin Application filed October 18, 1922,

The present improved alloy is one in which magnesium is the predominant element, such mnetal being preferably present in excess of 80 per cent, as prescribed in U. S. Patent No,

" 905,485 to listor et al., dated Jul. 20, W10. The other added metals incliulb copper, aluminum and cadmium, the copper being added in flll'lOlllltS greater than those of aluminum and cadmium.

As noted in Reinglass treatise on Alloys (see page 175), the French patent to Walter Ri'ihel, No. 407,814, dated October 12, 1909, such patent corresponding in part to his U.

S. Patent No. 982,022, dated January 17, 1.911., suggests-that the zinc in this patentees magnesium-zinc formula may be partly replaced by copper or entirely by aluminum-and copper. ()ue illustrative formula of the latter ternary alloy is as follows, viz, magnesium 90 per cent, copper 9 per cent and aluminum 1 per cent.

I have found that magnesium-copper alloys are not very strong and furthermore are not particularly good for casting purposes and that the'addition of a little aluminum, in accordance with the Riibel formula just cited, greatly improves both the strength and the casting )roperties of such magnesium-copper alloy. n the other hand, the addition of a little cadmium to such magnesium-copper alloy does not appreciably improve the alloy; in fact, it often gives a very inferior castin If, however, instead of dealing with sudh magnesium-copper alloy, we take a magnesiuiii-copper-aluminum alloyofapproximatelythe composition described by Riibel and add a small amount of cadmiumJ have found that an alloy is produced that is considerably better-than the original ternary alloy. In other words, the resulting quarternary magnesium-copper-aluminum-cadmium alloy presents superior qualities both from the standpoint of strength and toughness and that of casting and general workability.

The composition of my improved alloy will now be full described and particularly pointed out 1n the claims, it being understood that the following description sets forth but several of the various ways in which the principle of the invention may be carried out.

The ranges .of composition that have been found satisfactory for use in my improved quarternary alloy are as follows, viz, cop- I per lie 12 per cent (4 to 8 per cent being Serial No. 595,277. Renewed September 1, 1926.

preferred), aluminum 1 to 4 per cent (1 to 2 per cent being preferred), cadmium 1' to 4 per cent (2 to 3 per cent being preferred), and magnesium constituting the balance.

A specific formula that has proven very satisfactory, both in test and actual use, is as follows, viz, magnesium 92 per cent, c0 per 4: per cent, aluminum 2 per cent, cad mium 2 per cent. The physical properties of this particular alloy have been determined to be as follows, viz, tensile strength 20,000 to 22,000 lbs. per square inch; thermal conductivity 0.30; single-blow impact-toughness and Brinell hardness 45. As compared with other commercial light-metal alloys wherein magnesium is the predominant ingredient, my new alloy would appear to have approximately the same tensile strength combined with a somewhat greater toughness, as indicated by the single-blow impact number, a somewhat lower Brinell hardness, and a much higher thermal conductivity.

Accordingly, it would appear that the addition of cadmium to a ternary magnesiumcopper-aluminum alloy of the type in hand, wherein the amount of copper is" in excess of that of aluminum, materially increases the strength and toughness of the resulting product and so presents an effect that would be wholly unsuspected from the elfect of adding cadmium to a binar magnesium-copper alloy. It Will be understood that the physical properties of my improved alloy may be modified-by the additions of small amounts of other metals such as zinc and tin. Where zinc is thus employed, the amount thereof will desirably be kept within the range where such zinc will dissolve in the magnesium, i. e., enter into solid solution. With this in mind, the amount of zinc recommended is from 0.30 per cent to 0.65 per cent, only, while the amount of tin, where this metal is added, SllOLild not greatly exceed 1 per cent of the tota ()ther modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the materials employed, provided the ingredients stated by any of the following claims or the equivalent of such stated ingredients be employed.

'I therefore particularly point out and dismium, wherein the magnesium largely predominates and the amount of the copper ranges from approximately 3 to 12 per cent, the amount of copper exceeding that of aluminum and the latter as well as the cadmium being present in substantial amounts.

- 2. As a new product, an alloy consistin of magnesium, copper, aluminum and mium, wherein the magnesium is in excess of 80 per cent and the amount of the copper ranges from a proximately 3 to 12 per cent, the amount 0 copper being approximately twice that of aluminum and the latter as well as the cadmium being present in substantial of magnesium, copper, aluminum and cadcadmium from 1 to 4 per cent of the total.

4:. As a new product, an alloy containing magnesium, copper, aluminum and cadmium,

wherein the magnesium largely predominates, 25 the copper being from 4 to 8 per cent, the aluminum from Ito 2 per cent, and the cadmium from 2 to 3 per cent of the total.

5. As a new product, an alloy containing approximately 92 per cent of ma esium, 4 per cent of copper, 2 per cent of a uminum and 2 per cent of cadmium.

Signed by me, this 14 day of October, 1922.

JOHN A. GANN.