US 2810641 A
Description (OCR text may contain errors)
United States Patet PRECIPITATION HARDENABLE COPPER, NICKEL, ALUMINUM, ZIRCONIUM ALLOYS John S. Roberts III, Fairfax, Va.
No Drawing. Application December 22, 1954, Serial No. 477,130
6. Claims. (Cl. 75-159) This invention relates to alloys and is more particularly concerned with alloys having properties comparable to those of copper-beryllium alloys but which do not employ any beryllium.
Copper-beryllium alloys are very important industrially and for military purposes. Because of their non-magnetic properties, good electrical conductivity, high tensile strength, high degree of hardness, and their ability to be cast, wrought, forged or drawn, they have been found useful for many purposes, including various types of surgical instruments, electrical contact points, coil springs, cutting tools of various kinds, including non-magnetic knives for underwater naval operations, etc.
However, beryllium is one of the rare elements of the earths crust and is not available in suflicient quantities to permit its wide use as an alloy element. Moreover, its indicated use in the field of atomic energy has rendered its supply for other purposes even scarcer. The cost of this element is also very high which is another serious deterrent to its general use as an alloying element.
Accordingly, one of the objects of this invention is the provision of a berylliumefree copper alloy having physical properties similar to those of copper-beryllium alloys.
Another object of the invention is the provision of such a beryllium-free alloy which contains relatively inexpensive alloy elements.
A further object of the invention is the provision of such a beryllium-free alloy which contains elements in substitution of the beryllium which are relatively abundant.
A still further object is the provision of an alloy of the type mentioned in which the tensile strength and hardness can be greatly increased by relatively short heat treatments or cold working treatments or both.
These and other objects and advantages of the invention will appear more fully from the following description.
The beryllium-free alloy in accordance with this invention comprises essentially, copper, nickel, aluminum and zirconium in the approximate ratio of one part nickel to about 10 parts copper and fractional parts of both zirconium and aluminum. The alloy may also contain fractional parts of iron, silicon and carbon. The following percentages by weight are found to give generally satisfactory results:
Copper 82.2 to 89.1 Nickel 7.5 to 8.9 Aluminum 0.8 to 3.4 Zirconium 0.5 to 4.0 Iron 0.7 to 1.3 Silicon 1.0 to 1.6 Carbon 0.05 to 0.5
The alloy is a liquid at about 1085 C. and can be cast in molds and wrought to finished forms as in the case of fabricating copper-beryllium alloys. After casting, it is given the usual solid solution treatment by elevating the temperature to a point below the melting point ICC where elements of the alloy are in solid solution and then quenching in water. The tensile strength and hardness of the alloy at this point can be increased to a remarkable extent by precipitation ageing and cold working and, moreover, the ageing can be accomplished in a very short time.
An essential aspect of the present invention is the combined use of aluminum and zirconium in a copper-nickel alloy containing 1 part nickel to about 10 parts copper. An alloy of this type without the aluminum or without the zirconium fails to develop the desired properties. The combination of these two elements, namely, aluminum and zirconium, is absolutely essential and have what may be regarded as a synergistic effect in the development of the high tensile strength and hardness comparable to or greater than that of copper-beryllium. Thus, typically, an alloy containing 90.0% copper, 9.0% nickel and 1.0% zirconium, but no aluminum, had an initial hardness of only 70 Vickers, which increased to only 76 Vickers after ageing for 11 hours at 400 C. and to 79 Vickers after ageing for 2 hours at 600 C. Similar results are obtained with an alloy in which a similar percentage of aluminum is substituted for the zirconium. However, an alloy of 88.2% copper, 8.8% nickel, 1.0% zirconium and 2.0% aluminum had an initial hardness of Vickers after the solution treatment which increased to 216 Vickers (96 Rockwell B) after ageing 11 hours at 400 C. and to 231 Vickers (98-99 Rockwell B) after ageing 2 hours at 600 C. An alloy containing the same amount of copper and nickel, but 0.5% zirconium and 2.5% aluminum had an initial hardness of 111 Vickers after the solution treatment, which increased to 250 Vickers Rockwell B) after ageing for 11 hours at 400 C. and to 265 Vickers (2627 Rockwell C) after ageing for 2 hours at 600 C.
A preferred alloy in accordance with this invention is of the following compositions in percentages by weight:
Copper 83.4 Nickel 8.1
Zirconium 3 .8 Iron 1.0
This alloy, after casting and heating to 960 C. followed by quenching in water, showed a tensile strength of about 60,000 pounds per square inch and a hardness of 69 Rockwell B. When given a further treatment for only one hour at 500 C. followed by quenching in water, the tensile strength increased to 113,000 pounds per square inch and the hardness to 93 Rockwell B. It was found that the tensile strength and hardness could be further increased by cold working or additional precipitation ageing or both. For example, 50% cold working increased the tensile strength from 113,000 pounds per square inch to 186,000 pounds per square inch and the hardness was well above 93 Rockwell B. This tensile strength is comparable to the usual copper-beryllium alloys. An additional heat treatment for two hours at a temperature of 450 C. followed by quenching in water, increased the tensile strength still further to 195,000 pounds per square inch.
An alloy of the same preferred composition, following the solution treatment, had its tensile strength increased from 60,000 to 125,000 pounds per square inch after 25% cold working and to 142,000 pounds per square inch after 50% cold working.
The same preferred alloy, following the solution treatment, when age hardened for only 15 minutes at a temperature of 565 C. and quenched in water, had its tensile strength increased from 60,000 to 144,000 pounds per square inch and its hardness from 69 Rockwell B to 100 Rockwell B. When further treated by working to 25% reduction, the tensile strength rose even further to 156,000 pounds per square inch and when worked to a 50% reduction, the tensile strength rose to 162,000 pounds per square inch.
1. An alloy consisting essentially, by weight, of 82.2 to 89.1% copper, 7.5 to 8.9% nickel, 0.8 to 3.47% aluminum and .05 to 4.0% zirconium.
2. An alloy as defined by claim 1 having also 1.0 to 1.6% silicon, 0.7 to 1.3% iron and 0.05 to 0.5% carbon.
3. An alloy as defined by claim 1 which has been subjected to age hardening at least once at a temperature in the range of 400 to 600 C. for a period in the range of 15 minutes to 2 hours.
4. An alloy as defined by claim 1 which has been subjected to cold working.
5. An alloy consisting essentially of, by weight, 83.4% copper, 8.1% nickel, 2.2% aluminum and 3.8% zirconium.
6. An alloys as defined by claim 5 having also about 1.0% iron, 1.3% silicon and 0.1% carbon.
References Cited in the file of this patent UNITED STATES PATENTS 2,027,750 Munson Jan. 14, 1936 2,102,238 Pilling et al. Dec. 14, 1937 2,137,282 Hensel et al Nov. 22, 1938 2,143,914 Hensel et al. Jan. 17, 1939 2,430,306 Smith Nov. 4, 1947