US1760549A - Aluminum alloy - Google Patents

Description

30 num, magnesium Patented 27, 1930 UNITED STATES PATENT, OFFICE I TBUMZLN S. FULLER AND DAVID BASCH,'OF SGHENECT ADY, NEW YORK, ASSIGNORS TO GENERAL ELECTRIC COMPANY A CORPORATION OF NEW YOBK ALUMINUM ALLOY Io Drawing.

Our present invention comprises an improved castallo of aluminum zinc and magnesium, and it is the ob ect of our mvention to improve the physical properties of the cast alloy.

Heretofore cast aluminum alloys .containa ing copper have been improved by heat treatment. The improvement has been ascribed to the tendency of-certain components, par- 1o ticularly copper-aluminum particles, to be thrown out of solution from the aluminum during the slow cooling after the heat treatment. I

We have now discovered that aluminum alloy castings containing at least about 6% a heat treatment schedule which is hereinafter described in detail. The improvement due to heat treatment is especially marked in the case of aluminum alloys containing both zinc and magnesium and an even more marked improvement due to heat treatment is obtained when other alloying "elements such as iron are present. D

The improvement in mechanical properties due to heat treatment in an alloy of alumiand zinc, illustrates the benefits of our invention. A cast alloy comprising about 92.7 5 parts aluminum, about 6 parts zinc and about 1.25 parts magnesium, and excluding copper except as a negligible impurity has a tensile strength of about 26,- 000 pounds per square inch and a hardness of about 75 Brinell. When this alloy is heated to about 515 C. for about twenty-four hours, then is quenched in boiling water, and finally is aged either artificially at about 150 C. for

three hours or more, or naturally the tensile strength is increased to about 35,000 pounds per square inch and the hardness is raised to about 104 Brinell. v

Fuller Patent 1,273,762 of July 23, 1918, covers an aluminum alloy containing zinc, magnesium and iron, or various described equivalents. In accordance with this patent the cast alloy is mechanically worked, as by iorging, rolling, or drawing. We have dis- Application filed December is, 1923. Serial 110. 680,516. 7 covered that the physical properties of the magnesium 1.25%, has without heat treat-' ment a tensile strength of about 30,000 pounds and a hardness of 65 Brinell.

In accordancewith our inventionthis cast alloy is given the following heat treatment:

The alloy first is heated to a temperature of about 450 to 575 C. for about 24 hours and then is quenched, preferably in boiling water. Next the alloy is subjected to an aging treatment, ior example, by heating to a temperature of about 150 C. for about. one to three I hoursor more. Thereafter it may be allowed to cool naturally. As a result "of this heat treating schedule the properties of the cast alloy are materially improved. The tensile strength-is increased to 50,000 pounds and the hardness is raised to 115 Brinell. In place of iron, or in addition to iron, other alloying metals, including'silicon, may be added to the alloy of aluminum, magnesium and zinc.

In'this specification and in the claims, the terms quenching and a ing are intended to cover not only the speci c temperatures enumerated herein but also the known variations of these temperatures which are permissible under various conditions. Forexample, it is known that aging of an alloy can be carried out at a lower temperature if the length of the I aging step is correspondingly increased.

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

1. The method of improving the tensile strength and hardness of an aluminum alloy containing atfleast about six per cent zinc,

about one-half to two and one-half per cent 2. A heatrtreated alloy of aluminum being substantially devoid of cop er and containing about six per cent zinc, about one and onequarter per cent magnesium and two per cent 5 iron said alloy having a tensile strength of about 50,000 pounds per square inch and a hardness of about 155 Brinell but having otherwise substantially the properties of cast metal.

o 8. The method of imgroving the tensile strength of a cast alloy w ich is substantially devoid of. copper but contains more than 80% aluminum, at least about 6% zinc and at least about magnesium, which consists 15 in heatingltlhe alloy between 450 C. and 57 5 (3., quenc 'ng the alloy and then aging it at a temperature of about 150 C.

In witness whereof, we have hereunto set, our hands this 12th da of December, 1923. so TR S. FULLER.

- 7 DAVID BASOH.