US1352271A - Alloy - Google Patents

Description

Z. IEFFRIES AND W. A. GIBSON.

ALLOY.

APPLICATION FILED .IULY 30,1919.

Patented Sept. 7 1920.

`0f from 3% to 4%.

UNITED STATES 'PATENT OFFICE,`

ZAY JEFFRIES AND WILLIAM A. GIBSON, OF CLEVELAND, OHIO, ASSIGrNOItS TO THE ALUMINUM CASTINGS COMPANY, OF-CLEVELAND, OHIO, A CORPORATION OQHIO.

ALLOY.

Specicatin of Letters Patent.

Patented sept. 7, 192e.

,AppIieation led July 30, 1919. Serial` No. 314,261.

To all whom t may concern Be it known that we, ZAY JEFFRIES and WILLIAM A. GIBSON, citizens ofthe United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented Certain new and useful Improvements in Alloys, of which the following is a specification, reference being had therein to the accompanying drawing.

This invention relates to improvements in aluminum alloys and is concerned especially with aluminum alloys containing zinc, copper and iron.

One object of the invention is to provide anA aluminum v alloy containing zinq having physical properties, especially tensile strength and ductility, superior to those ossessed by aluminum-zinc alloys hereto ore known.l

. Another object of the invention is to provide an aluminum-zinc alloy having superior physical properties in combination with ease of preparation and good casting, machining and workingv qualities.

Binary alloys of aluminum and zinc have been extensively investigated and it has long been known that the elfect of zinc when added to aluminum is to produce rela` tively close grained and non-porous castings. By many it has been supposed that these aluminum-zinc alloys essentially are subject to excessive corrosion and offer relatively slight'res'istance to shock. It is now known, however, that these objectionable characteristics are entirely obviated when suitable care is taken to insure uniform mixing of the constituent metals in proper proportions.

'lhe ternary alloys of aluminum, zinc and copper have been only slightl investigated so far as we are aware. heir physical properties, however, so far as known, are a pre'ciablybetter than those of the binary a uminum-zinc alloys. We have found that an aluminum alloy containing about 8% zinc and 3% copper has a tensile strength ranging from 20,000 pounds to 26,000 pounds per square inch, and an elongation (Here, as elsewhere in this application, the composition percentage is by weight)..

Ve have discovered that these physical properties can be very greatly improved by the addition to a ternary alloy ofthe above composition of from 0.5% to 1.5% of iron. While the proportions of the various constituents may vary through a considerable range and still retain in substantial measure the advantages of this four part alloy,-

the composition which we prefer to employ is one containing from 6% to 8% zinc, from 2.5% to 3.5% copper, from` 1% to 1.5% iron,

v andthe remainder aluminum. Alloys withbetween 55 and 60, and specific gravitiesless than 3.0. By increasing the percentage of zinc and decreasin that of aluminum greater tensile strengt is obtained but at the sacrifice of ductility.

An alloy of the preferred composition can be made up in various ways known to those skilled in the art. One successful method is as follows:

First is prepared a rich'alloy-containing three parts of copper to one part'of iron together with a sufficient amount of aluminumto reduce` the melting point ofthe alloy to approximately that of aluminum.

The calculated amounts of aluminum and' of the above rich alloy are melted together and the calculated quantity of zinc is then adder?. While stirring. After thorough stirring the metal is heated to the desired pouring temperature. This alloy may be cast equally well in sand molds and permanent molds and by reason of the zinc content, which renders the melt quite fluid, it will completely and quickly till the mold, even where there are thin sections. The alloy is easy to make because no extremely` high tempera-tures are required( Castings of this alloy are very dense, have good machining qualities and are not ea'sily corroded o1- aifected by shocks.

We have -found that it is not advantageous to heat treat these alloys, for while heat treatment may in some cases increase tensile strength somewhat, it results 1n .a relativel greater decrease of the elastic limit. or most purposes the lowerlng of the elastic limit would outweighl the advantages incident to any increased tensile .amounts of zinc and 1% added iron.

strength so that, as stated, heat treatment of the alloy is not ordinarily advantageous.

The accompanying drawing shows graphbrokelrline curves represent the alloys Without iron and the full linecurves represent.

the alloys with iron. The horizontal scale at the bottom represent the per cent. of zinc, the Vertical scale at the left, tensile strength I and the vertical scale atv the right, the per cent. elongation. It will be observed that the addition of 1% iron to the ternary alloy markedly increases both the tensile strength and the elongation. With 7% to 8% Zinc the alloy presents a highly advantageous combination of tensile strengths ranging from over 27,500 pounds to over 28,500 pounds per square inch and elongation ranging `from over 6% to over 7%, whereas the ternary alloy without the iron has a tensile strength ranging well below 24,000 pounds per square inch and an elongation ranging well below 4%.

As has already' been indicated, if the use ofthe alloy requires a still higher tensile strength this can be obtained at the sacrifice of ductility, by increasing the quantity of zinc above, say 8%, and maintaining the iron and copper contents. However, these aluminum alloys containing more than 8% zinc with 1% .iron and 3% copper are not only stronger but also more ductile than the aluminum alloys containing zincA and copper alone. For example, as will be noted on reference to the drawing, with 15% zinc and 3% copper and 1% added iron the tensile v strength is 37,000 poundsper square inch,

and elongation 2.5% whereas the saine composition without the iron has a tensile strength of 32,000 pounds per square inch and an elongation of 1.8%.

As 1s well known to those having commercial experience W1th alumlnum, it 1s impossible to secure the metal in commercialV quantities free from impurities, notably iron and silicon. The iron thus present will, of course, be taken account of in introducing additional iron; and care should be taken to keep the amount of silicon present as low asY possible. It may be observed in connection with the vvalues mentioned for tensile strength and ductility, that in the case of castings made from our improved alloy the tensile strengths increase and the ductility decreases slightly as the castings age.

In the foregoing description We have indicated the preferred range of compositions and the preferred method of preparing our improved alloy, but it isto be understood that our invention is not limited in these respects except as specified in the appended claims. f

What We'claim is:

1. An alloy 'containing aluminum, copper, zinc and iron, the copper content being from 2% to 5%, the zinc content being from 4% to 25%, the iron content being from 0.6% to 1.8%, and the aluminum making up the remainder.

2. An alloy containing aluminum, copper, zinc and iron, the copper content being from 2% to 5%, the zinc content being from 4% to 16%,'the iron content being from .6% to 1.8%, and the aluminum making up the remainder.

3. An alloy containing aluminum, copper, r/iinc and iron, the copper content being from 2.5% to 3.5%, the zinc content being @om 6% to 8%, the iron content being from 0.8% to 1.5%, and the aluminum making up thel remainder.

4. An alloy of aluminum, copper, zinc and iron containing approximately A88.7% aluminum, 3% copper, 1.3% iron and 7% zinc.

5. An alloy containing aluminum, copper, zinc and iron, the copper content being approximately 3%, the iron content being approximately 1.3% and the Zinc content ranging from 4% to 25%, and the aluminum making up the remainder.

6. An alloy containing aluminum, from 2% to 5% of copper, from .5%` to 1.5% of iron and zinc and having a specific gravity less than 3.0.

In testimony whereof, we hereunto affix cur signatures.

ZAY JEFFRIES. WILLIAM A. GIBSON

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