US2213397A - Alloys - Google Patents

Description

Patented Sept. 3, 1940 I ALLOYS Edwin F. Kingsbury, Rutherford, and Howard T.

Reeve, Millbum, N. J., assignorsto Bell Telephone Laboratories, Incorporated, New York,

N. Y., a corporation of New York No Drawing. Original application July 10, 1937,

Serial No. 152,993. Divided and this application October 18, 1938, Serial No. 235,560

8Claims. (c1. lie-11.5)

This is a divisional application of U. S. Patent are positioned so that an atom of one element 2,148,562, Serial No. 152,993 filed July 10, 1937 is nearer the atom of the other element. The granted to E. F. Kingsbury and H. T. Reeve on lattice structure of the ordered state is the body February 28, 1939. centered cube, while the lattice structure of the This invention relates to contacting alloys and random. state is the face centered cube. The more particularly to c pp r-P dium alloys copper-palladium alloys as usually prepared are employed for contacts on electrical apparatus. in a random state, or in any case, are only An object of this invention is to increase the partially ordered. Certain characteristics of efficiency and prolong the usefulness of contacts copper palladium alloys undergo profound employed on electrical apparatus. changes when converted from the random to the 10 The contacts f e cal p a us. e pec y ordered state. The electrical resistivity of an relay contacts-are subjected to severe conditions alloy comprising 47.2 atomic per cent palladium in use. The minute sparking in the operation and 52.8 atomic per cent copper (60 per cent of t contacts of relays and other pp a palladium and 40 per cent copperby weight) in causes the building-up of the material on the the ordered condition is less than approximately 15 contacts to render ultimately the relay inoperaone-tenth of that in its random state. The tive. Various materials which withstand these specific resistivity of the ordered alloy comprising severe conditions have been suggested. For ex- 47.2 atomic per cent palladium and 52.8 atomic ample, E. F. Kingsbury in U. S. Patent 1,779,602 per cent copper .is less than 4x 10- ohm-cm.

granted on October 28, 1930, has proposed the This resistivity is considerably less than that of 2.0 1156 Of Copper-Palladium d t r a ys for palladium itself in spite of the fact that the e ec a c t a oy of Palladiumalloy is almost in the center of the binary series. pp while p s ss lat v re d m r m The ordered alloys are substantially harder than cessive oxidation and in general satisfactory as the corresponding alloys in the random state and a contacting material are somewhat susceptible, the thermal conductivity is substantially greater 25 as ordinarily prepared, to the building-up in the ordered alloys. This greater hardness is phenomena in which material is transferred from of value when contacts are subjected to constant O e Co t to a o e battering action such as that which obtains in The major factors which are correlated with high speed telegraph relays. The ordered structhe transferring of the material of one contact ture of the alloys also has beenffound to result 30 to that of another are the thermal and electric in decreased chemical corrosion on exposure, to conductivity of the alloy. An alloy having a hydrogen sulphide and sulphur dioxide. The higher thermal and electric conductivity than decreased resistivity, the increased thermal con-.- h f another l y mp ng the same conductivity, hardness and resistance to corrosion stituents is less prone to the transferring and contribute to make alloys of copper-palladium in 36 building-up in needle-like fashion of the material the ordered state extremely desirable as contact 'of one contact on that of another. alloys for relays and other electrical apparatus.

In accordance with this invention copperone method of preparing the copper-palladium P l m alloys are P p ed which have relaalloy in the ordered state is to cold work the 40 tively high thermal and electrical conductivities alloy and subsequently heat treat it within a 40 and which are resistant to corrosion such as that temperature range of 275 C. to 450 C. The caused y Sulphur dioxide- F her, these alloys cold working may be effected by reducingthe when employed for contacts on relays and other cross-sectional area of the alloy in the order of electrical apparatus manifest greater resistance less than 50 per cent of that of the original. For

- to the transfer of metal from one contact to example, an alloy'comprising per cent atoml- 45 another. cally of palladium and 50 atomic per cent of Copper-palladium alloys, and more particularly copper (62.7 per cent palladium and 37.3 per alloys comprising 38 to 50 atomic per cent of cent copper by weight) in the form of a wire .050 palladium and the remainder chiefly copper exist inch in diameter, is reduced to a diameter of .005

50 in two extreme physical conditions, one, in which inch. This wire is then wound on a form, leads 60 the atoms of the two elements are distributed at are welded on the. wire for the determination random, and the other in which the distribution of the resistance thereof and the form placed in is ordered. In the ordered condition, the two a quartz tube which is maintained at a temperaelements are in preferred positions with respect ture of 280 C. This heat treatment may be to each other, or more concretely, the elements performed in vacuum or in the presence of an 55 inert gas which does not react with the copperpalladium alloy. The resistivity of the wire is determined from time to time in order to ascertain whether the transformation from the random state to the ordered state has been effected. A period of 15 to 30 minutes has been found satisfactory for this size of wire. Usually, the greater the degree of hard working prior to heating, the lesser time is required for the transformation. In any event the alloy is left in the furnace until the transformation is effected. As ascertained by resistance measurements, the specific resistivity for this particular alloy in the ordered state is 4.1 10 ohm-cm. After the transformation has been accomplished, the wire in the furnace is permitted to cool slowly therein to room temperature. With a wire .005 inch in diameter, the transformation from the random to the ordered state occurs in less than seven minutes at a temperature range of 290 C. to 330 C. Although the transformation is produced in this period, the alloy is preferably subjected to the heating for a longer time, such as 15 to 30 minutes. The transformation may also be ascertained by X-ray examination although the resistivity determination is more convenient.

While two specific alloys of copper-palladium have been noted, any other alloy of copper-palladium, consisting of 38 to 50 per cent atomlcally of palladium (50.7 to 62.7 per cent palladium by weight) and the remainder chiefly copper, may be treated in like manner to change them from the random to the ordered state. The period of heating in each case is relatively short and can be easily ascertained by resistivity measurements.

While preferred embodiments of this invention I have been described, various modifications theren LI in may be made without departing from the scope of the appended claims.

What is claimed is:

1. Themethod of forming an improved contact alloy consisting of 50.7 to 62.7 per cent palladium by weight and 49.3 to 37.3 per cent copper by weight, said method comprising cold working approximately 280 C. to effect the transformation of said copper and. said palladium from a random to an ordered state and slowly cooling said alloy to room temperature.

3. A contact material consisting of 50.7 to 62.7

per cent palladium by weight and 49.3 to 37.3 per cent copper by weight, said alloy being prepared by cold working and subsequent heat treatment at a temperature between 275 C. to 450 C. to convert said palladium and said copper from a random to an ordered state.

4. A contact material consisting of approximately 60 per cent palladium by weight and approximately 40 per cent copper by weight, said alloy being prepared by cold working and subsequent heat treatment at a temperature between 275 C. to 450 C. to convert said palladium and said copper froma random to an ordered state.

5. A contact material consisting of approximately 62.7 per cent palladium by Weight and approximately 37.3 per cent copper by weight, said alloy being prepared by cold working and subsequent heat treatment at a temperature between 275 to 450 C. to convert said palladium and said copper from a random to an ordered state.

6. The method of forming an improved contact alloy consisting of 50.7 to 62.7 per cent palladium by weight and 49.3 to 37.3 per cent copper by weight, said method comprising cold working said alloy by reducing the cross-sectional area thereof to the order of less than per cent of that of the original and heat treating said alloy at a temperature between 275 C. and 450 C. to change the atomic relation of said palladium and said copper from a random to an ordered state.

7. The method of forming an improved contact alloy consisting of 50.7 to 62.7 per cent palladium by weight and 49.3 to 37.3 per cent copper by weight, said method comprising'cold working said alloy, heating said alloy to a temperature at which it is converted from a random to an ordered state, maintaining said alloy at said temperature for a time sufiicient to cause conversion to the ordered state and cooling said alloy.

8. A contact element consisting of 50.7 to 62.7 per cent palladium by weight and 49.3 to 37.3 per cent copper by weight, said alloy being prepared by cold working, subsequent heating to a temperature at which said alloy is converted from a random to an ordered state for a time sufllcient to cause conversion to the ordered state, and subsequent cooling.

EDWIN F. KINGSBURY. HOWARD T. REEVE.