US1920249A - Aluminum base alloy containing copper, nickel, and silicon - Google Patents

Description

Patented Aug. 1, 19.33

ALUMINUM. BASE ALLOY CONTAINING COPPER, NICKEL, AND SILICON Walter A. Dean, Cleveland, Ohio, assignor to Aluminum Company of America, Pittsburgh, 'Pa., a Corporation of Pennsylvania No Drawing. Application July 22, 1931. Serial No. 552,557

3 Claims. (01. 15-1.)

This invention relates to aluminum base alloys designed to meet the problems encountered in the manufacture of articles which must withstand high temperatures without-plastic de- 5 formation or a comparatively large loss of strength, as for example, the manufacture of pistons for internal combustion engines, more particularly the invention relates to aluminumsilicon-copper-nickel alloys, with or without one or more of the elements titanium, molybdenum, tungsten, manganese, chromium and iron.

Somewhat similar alloys have already been disclosed in a copending application of R. S. Archer and L. W. Kempf, Serial No. 403,353, filed October 29, 1929. The present invention constitutes an alloy of this class of greatly improved tensile strength in the cast condition, higher impact resistance at elevated temperatures, and more refined crystalline structure.

0 In the above-mentioned copending application, aluminum base alloys were disclosed and claimed containing 6 to 8 per cent nickel, 6 to 8 per cent silicon, and 6 to 8 per cent copper and characterized in particular by low thermal ex-.

pansivity, improved strength at high temperatures, and high modulus of elasticity. Th'ese desirable properties are commercialized specifically into pistons for internal combustion engines or other uses where the articles are subjected to stress at relatively high temperatures. I have found that if the composition be modified so that the alloy contains less than 6 per cent but not less than about 2 per cent of nickel, the tensile strength in the cast condition is raised;

the crystalline structure 'is more refined, and the ductility of the alloy is increased, without material impairment of any of the advantages which characterized the former commercial composition disclosed in the aforesaid application. I

L0 have also found that the copper and silicon contents can be decreased to about 5 per cent without impairing the advantageous properties of the alloy.

As an example, an aluminum base alloy containing 'l per cent copper, '7 per cent silicon, and 7 per cent nickel has an impact value of about 39 foot pounds per square inch at 600 degrees Fahrenheit, and the impact value of one of my alloys containing 7 per cent copper, '7 per cent silicon, and 4 per cent nickel under the same conditions is foot pounds per inch or an per cent increase in-impact resistance. This comparison is derived from the results of a series of liightemperature tests made on a Charpy impact testing machine adapted to high temperature work. A high impact resistance at elevated temperatures signifies an ability to withstand severe shock at elevated temperatures, a property very useful when the alloy used is in the form of a piston in-internal combustion engines.

The tensile strength of an alloy of '7 per cent copper, 7 per cent nickel and 7 per cent silicon is about 17,000 pounds per square inch in the ascast condition. The tensile strength of one of my improved alloys in which the nickel is reduced to 4 per cent, the copper and silicon remaining at 7 per cent each, is about 26,000 pounds per square inch.

I have discovered, in addition, that the hardness of my alloys at elevated temperatures may be improved by adding from about 0.01 per cent to 1.0 per cent of a high melting point metal, for instance titanium, molybdenum, tungsten, manganese, chromium, or iron, without sensibly impairing other useful properties of the alloys 75 and even, in some cases, effecting considerable improvement in characteristics such as grain size. More than one of these high melting point metals may be used in combination provided their total amount does not exceed about 1 per cent of the whole.

The alloys which are the subject of the present invention may be heat treated for the purpose of improving their tensile and hardness properties or they may be otherwise thermally treated for the purpose of removing strains or stabilizing volume changes. For such purposes, the heat treatment and other thermal processes well known to those skilled in the art may be temperature solution heat treatment and the lower temperature aging treatment now widely recognized as being beneficial in the case of certain aluminum base alloys.

The term "aluminum-sllicon-copper-nickel alloy is used herein and in the appended claims as including the following, and none other: (a) Alloys consisting of the four elements named, in the proportions stated in the claims; and (1)) Alloys consisting of the four elements named, in the proportions stated in the claims, and one or more of the metals titanium, molybdenum, tungsten, manganese, chromium and iron, in total amount from about 0.01 to 1 per cent.

Having thus described and explained my invention, what I claim is- 1. An aluminum-silicon-copper-nickel alloy in which the elements named are in substantially thefollowing proportions: Nickel2 to 4 per cent,

copper 5 to 8 per cent, silicon 5 to 8 per cent, and aluminum 7'! to 88 per cent.

2. An aluminum-silicomcopper-nickel alloy in which the elements named are in substantially I not less than 81 per cent.

4. An aluminum-silicon-copper-nickel alloy in which the elements named are in the proportion of nickel 4 per cent, copper '7 per cent, silicon 7 per cent, aluminum at least 81 per cent; the alloy containing also at least one metal of the class composed of titanium, molybdenum, tungsten, manganese, chromium and iron, the total amount of metal of said class being about 0.01 to 1 per cent.

5. A piston formed of an aluminum base alloy consisting of aluminum, about 5 to 8 per cent silicon, about 5 to 8 per cent copper, not less' than about 2 but less than 6 per cent nickel, aluminum at least 77 per cent, and at least one metal of the class composed of titanium, molybdenum, manganese, chromium, tungsten and iron, the total amount of metal 01' said class being from about 0.01 to 1 per cent.

6. A piston formed of an aluminum-silicone,

copper nickel alloy in which the elements named are in substantially the following proportions: nickel 4 per cent, copper 7 per cent, silicon 7 per cent, and aluminum at least 81 per cent.

. WALTER A. DEAN.