US1932844A - Aluminum alloys - Google Patents

Description

Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE ALUMINUM ALLOYS Pennsylvania No Drawing. Application September 21, 1932 Serial No. 634,162

4 Claims.

This invention relates to aluminum base alloys which have excellent properties at elevated temperatures, which are generally adapted to foundry purposes and which arei nsensitive to the 5 common impurities found in commercial aluminum.

A good foundry alloy which will retain a substantial proportion of its physical and tensile properties at elevated temperatures is constantly being searched for in the field of light metals. By light metals are not meant the ordinary aluminum base alloys but only such of those alloys as contain substantial amounts of a metal lighter than aluminum so as to compensate in the alloy for the addition of metals heavier than aluminum. To provide such an alloy of good foundry characteristics and excellent strength at high temperatures is the object of this invention.

The aluminum base alloys containing magnesium are lighter than aluminum. They should therefore be excellent material from which to manufacture reciprocating parts which oper-; ate at elevated temperatures were it not for the fact that these alloys at elevated temperatures (such as 400 to 700 Fahrenheit) do not have the strength, the ductility 'and the hardness which are so often necessary. Moreover, the binary aluminum-magnesium alloys are somewhat lacking in the required foundry characteristics.

We have discovered, after extensive experimentation, an aluminum base alloy containing magnesium which fulfills, to a large extent, the requirements above mentioned. This alloy is one containing 3.0 to 8.0 per cent by weight of magnesium, 0.5 to 4.0 per cent by weight of manganese, 0.5 to 4.0 per cent by weight of nickel, and 0.5 to 4.0 per cent by weight of cop-' per, the balance being principally aluminum. This alloy, we have discovered, has very good foundry characteristics, being capable of use either in sand or permanent molds. The alloy is light, is strong and hard and possesses these latter properties to a substantial extent at high temperatures. The alloy is, moreover, stable in its properties over long periods at high temperature and is therefore a very dependable engineering material. Also the alloy is insensitive to impurities, which is to say that its properties are not materially affected by the varying amount of impurities, such as iron, which may be found in the commercial aluminum from which it is usually made.

The tensile strength of the alloy is high at elevated temperature and its elongation, while not as high as might be desired, is adequate when ductility is not a leading property. Examples of the strength and ductility of the alloys will be found in Table I where are listed the tensile strength and elongation of two sand castings made of the alloy, annealed for 4 hours at 700 Fahrenheit, cooled to 600 Fahrenheit, and finally tested at the latter temperature.

For comparison it may be stated that a binary aluminum-magnesium alloy containing 6 per 75 cent magnesium and in sand cast form had, after a similar thermal treatment, a tensile strength of only 15,400 pounds per square inch and an elongation of 5.5 per cent in 2 inches.

The superior strength of our new alloys at elevated temperatures may be shown by comparison of one of the alloys in sand cast form with a sand casting made of a well known aluminum alloy containing copper. Sand castings made of an alloy containing 6 per cent magnesium, 5 1.0 per cent manganese, 1.5 per cent nickel, and 2.0 per cent copper, balance aluminum, were annealed for 4. hours at 700 Fahrenheit, the tem perature was then reduced to 600 Fahrenheit and the alloys tested at that temperature. Similar treatment was afforded sand castings made of an alloy containing 10 per cent copper, 0.2 per cent magnesium, and 1.2 per cent iron, balance aluminum, and these castings were similarly tested. The results are shown in Table II.

' Table II Tensile strength 5%? pounds ga- Alloy composition per tion square inch 0 as 67m 1.07 Mn 1.5 7 Ni 2.07 Cu 20,000 1.0 a 109; Cu 0.27: Mg 1.27.; Fe 15,300 2.0

The aluminum-magnesium-manganese-nickelcopper alloys to which this invention refers have certain preferred forms. Within the composino tion limits above described, the alloys are satisfactory for most purposes, but we have found the best combination of properties in alloys containing 3.5 to 6.5 per cent by weight of magnesium, 0.5 to 2.0 per cent by weight of manganese, 0.5 to 3.0 per cent by weight of nickel, and 1.0 to 2.5 per cent by weight of copper, balance principally aluminum.

The alloys which are herein described may be made by any of the usual methods of compounding alloys, care being taken, of course, not to overheat or dross the metal during alloying.

Another property of these alloys is their improved fiuidity as compared with the alloys which have, heretofore, been widely 'used as a material for parts operating at elevated temperatures. Comparative tests, based upon the distance that the molten alloy, originally heated to a given temperature, will flow through a spiral formed in a sand mold, have shown that our novel alloys are very superior with respect to fluidity.

The aluminum used in the manufacture of the alloys may be of the highest purity or it may contain amounts of usual impurities, and the term aluminum as used herein and in the claims designates the aluminum of commerce. It is an incidental property of our alloys that the presence of iron in amounts as high as 2 per cent by weight is not harmful to the high temperature properties of the alloys and, therefore, a wide choice between the various grades of commercial aluminum is possible.

We claim:

1. A metallic alloy consisting of 3.0 to 8.0 per cent by weight of magnesium, 0.5 to 4.0 per cent by weight of manganese, 0.5 to 4.0 per cent by weight of nickel, and 0.5 to 4.0 per cent by weight of copper, the balance being substantially aluminum.

2. A metallic alloy consisting of 3.5 to 6.5 per cent by weight of magnesium, 0.5 to 2.0 per cent by weight of manganese, 0.5 to 3.0 per cent by weight of nickel, and 1.0 to 2.5 per cent by weight of copper, the balance being substantially aluminum.

3. A metallic alloy consisting of 6.0 per cent by weight of magnesium, 1.0 per cent by weight of manganese, 1.5 per cent by weight of nickel, and 2.0 per cent by weight of copper, the balance being substantially aluminum.

4. A metallic alloy consisting of 6.0 per cent by weight of magnesium, 1.0 per cent by weight of nickel, 0.5 per cent by weight of manganese, and 1.0 per cent by weight of copper, the balance being substantially aluminum.

WALTER A. DEAN. LOUIS W. KEMPF.