US2163224A

US2163224A - Method of production of allots

Info

Publication number: US2163224A
Authority: US
Publication date: 1939-06-20
Anticipated expiration: 1956-06-20

Description

Patented June 20, 1939 U KTE STATS PATENT FFICE METHOD OF PRODUCTION OF ALLOYS No Drawing. Application October 25,

Serial No. 170,850

16 Claims. (cl. 75-22 My invention relates to a method of production of alloys of certain metals with metals of the titanium group of the periodic table of elements and more especially the "A sub-group of the B fourth group of the periodic table of elements.

It has heretofore been known that copper may be alloyed with metals of the titanium group, the common method being to add the alloying element to a molten bath of the other element. This method requires the use of special fluxes to minimize the oxidation of the alloying element and is further complicated by the fact that there is a very great difference in the melting points and in the specific gravity of the alloying metals. Copper has a specific gravity of 8.94 and a melting point of 1083" C., whereas zirconium, for example, has a specific gravity of 6.4 and a melting point of 1700 C. The other metals of the same group also have very high melting points and densities either much lower or considerably higher than that of copper.

When such an element as titanium, which has a specific gravity of 4.5 and a melting point of approximately 1800 C., is added to the molten bath of copper it does not go into solution rapidly enough and, owing to its low density, rises to the to where it is at least partly oxidized. The losses in titanium in some cases may reach almost 90% of the added pure metal. The use of special fluxes forming a liquid blanket on the surface of the molten copper improves to a certain degree this condition, yet it does not give entirely satisfactory results. The great difference in the densities between copper and the alloying elements of the titanium group can not be changed and causes a production of alloys with an uneven distribution of the added element.

The present invention relates in a specific aspect to a method of production of alloys of copper with metals of the titanium group which avoids the difficulties of the known processes and enables me to produce cast alloys having uniform dendritic structure throughout, the alloys being formed from powdered metals and at relatively low temperatures. In a broad aspect, however, the invention relates to a method of production of alloys of copper, nickel and silver with metals of the titanium group, as I have found that nickel and silver share with copper the characteristics necessary to the production of alloys according to the process.

Generaly speaking, the characteristics of copper, silver and nickel, which enable me to form alloys of these metals with metals of the titanium group in the manner hereinafter specified, resides in the fact that they have a definite chemical affinity for the metals of the titanium group and form therewith low melting point eutectic alloys, which in the presence of hydrogen form liquid layers around the grains of the titanium metals.

It is known that copper in an atmosphere of hydrogen can flow by capillarity and cover iron with a thin layer or penetrate almost microscopic cracks, yet to take advantage of the same property of copper to cover fine particles of titanium or any other metal of the titanium group ordinary hydrogen is not sufiiciently pure. Titanium, for example, is so easily oxidized at high temperatures that the least traces of oxygen or nitrogen will be suflicient to cover the surface of the titanium particles with a layer of oxide and nitride, which will prevent the diffusion of copper into the titanium. Even with hydrogen of the high degree of purity which it is possible to produce according to modern methods, its use in a method analogous to that disclosed herein would not be successful. It would be impossible to prevent the contamination of the pure hydrogen from oxygen and nitrogen evolving from the metals themselves. Thus, as is well known, the surface of copper particles is commonly covered with a variable amount of copper oxide which would be reduced during the process, the liberated oxygen combining with the hydrogen to form steam which, in turn, would be reduced by the titanium.

I have found that to accomplish the desired results the atmosphere of hydrogen must evolve from the powdered material itself and should be produced in sufiicient volume. When the hydrogen evolves from the powdered titanium group metal it sweeps from the mass all traces of oxygen and nitrogen entrapped in the powdered material and permits the copper, nickel or silver to wet the grains" of powdered titanium group metal and thus to form a low melting point alloy on the surface of the titanium group metal, which protects the latter against oxidation during the remaining. steps of the process.

To fulfil the condition that the powdered titanium metal contain hydrogen, which will evolve during the operation of the process to form nascent hydrogen, I may use hydrides of the titanium metals prepared in accordance with the teachings of my prior United States Patent No. 2,038,402, or

e the hydrogen may be contained in the metal by temperature and gas pressure. Every one of these metals absorb such a large volume of hydrogen as to form a true hydride which can be represented by a chemical formula such as TiaHa, TlHz, Zl'Ha, HfHa or 'I'hH2. For certain purposes, for examplewhere the resulting ingot should befree from blow holes, it is necessary to use one of these hydrides in absolutely dry and partly de-gassed state. The chemical analysis of such material indicates the much lower hydrogen content than in a true hydride designated for instance by such a chemical formula as ZrHa. It is quite likely that every particle of the powdered material in such a case is not a true hydride but a solid solution of a hydride in a metal. In some cases the hydrogen content is still lower and the material may be'designated merely as a metal containing hydrogen.

I do not commit myself to the above theory as to the manner in which hydrogen may be contained in the powdered metals of the titanium group, as whatever the theory may be the practical results are the same. Whether I use a true hydride, a partly de-gassed hydride or a metal containing hydrogen in occluded form, if the volume of gas evolving therefrom is sufficient it accomplishes the desired purpose of effectively shielding the materials before the reaction takes place and permits the copper, nickel or silver to completely wet. or flow around the grains of the titanium group metals and protect them against oxidation during the remainder of the process.

As a further aid to the understanding of the improved process I will now describe the formation of an alloy of copper with titanium. Powdered titanium hydride, prepared by the method described in the specification of my prior Patent No. 2,038,402, is thoroughly mixed in'a ball mill with the desired amount of copper powder. The mixture may be placed in an alundum crucible and the latter introduced into a vacuum furnace in which the temperature is raised gradually up to 1000 C., that is, belowthe melting point of copper, the vacuum being maintained within the furnace by means of a suitable'pump. As the temperature rises above 350 C., the titanium hydride begins to dissociate and nascent hydrogen sweeps from the powdered mass all remaining traces of oxygen and nitrogen entrapped in the powdered material and the gradual sintering of copper particles draw all the particles into a compact mass.

The nascent hydrogen evolving from the titanium hydride provides a protective atmosphere for each individual particle of titanium during the first stage of theprocess and enables the copper to form a protective layer of liquid copper-rich alloy around each particle of titanium, the protective layer of liquid copper-rich alloy during the second stage of the heat treating process, when the nascent hydrogen has. been entirely withdrawn, acting as a protective agent or blanket for the titanium.

The effect of the mutual protecting of cop- Qer and titanium hydride is especially easy to observe in the preparation of high titanium copper alloys. For instance, 70% titanium-30% copper can be obtained in powdered form, and if the heat treatment is carried short time every individual grain exhibits the above eifect. Further heat treatment, however, induces the diffusion of copper into titanium producing a uniform alloy of titanium copper.

on for only a' The copper titanium alloys are produced by my method at a temperature considerably lower than the melting point of either of the metals. Nevertheless they possess a uniform composition. The uniform distribution of the alloying element is first of all assured by mixing the powdered materials in the ball mill. Furthermore, since the materials are sintered at a temperature below the melting point of copper, this heat treatment does not alter the uniform distribution of the particles with a different density through the mass of the treated material. In the last stage of the heat treatment during which copper diffuses into every individual particle of titanium and forms a low melting point alloy, the resulting liquid is of the same density throughout the whole mass, therefore eliminating any possibility of segregations.

Copper titanium alloy containing 15% of titanium was sintered and liquified by the treatment of a powdered mixture of copper and titanium hydride at 960 C. The metallographic tests on the obtained alloy showed that the alloy consists of a uniform dendritic structure throughout the mass of the ingot.

The alloys of copper zirconium and copper thorium have been obtained by the same method. The temperature of treatment however rises slightly with the rise of the melting point of the alloying element. Copper zirconium alloy, for instance, can be obtained in cast state by treatment at 1000 C. and copper thorium alloy at 1075 C. I

The addition of large percentages of the alloying element 60-80% of titanium for example, produces alloys of a higher melting point which if treated at 1000 C. are obtained not in the form of a cast ingot but in the form of a sintered sponge which is readily crushed into a fine powder.

The addition of a metal of the titanium group to copper imiparts considerable hardness and increases its resistance to corrosive and abrasive agents. The alloy of copper containing 25% of zirconium can not be cut with the hack saw. These alloys, therefore, are finding useful applications where increased hardness and toughness of copper is desirable.

Copper forms alloys in the described manner with the best results. Yet it is not necessary for copper to be in chemically pure state. It can contain other elements in a state of solid solution and still produce similar results. However, when such an element as nickel is present in copper in considerable percentage, the temperature of formation of alloys is higher. The percentage of nickel in copper can be varied in wide limits since nickel forms, with copper, a continuous series of solid solutions, and in spite of the fact that it usually is classed in a different group of elements, in this particular case it acts in a similar way to copper. For example, I have formed cast alloys of nickel and zirconium by heating the powdered mixtures of nickel and zirconium hydride to the temperature of 1200 C. which is very much lower than the melting point of nickel. These results were obtained due to the formation of low-melting point eutectic alloy which, as in the case of copper, forms a liquid layer around the grains of zirconium.

The formation of alloys of nickel and silver with metals of the titanium group is carried out in a manner similar to that described in connection with the copper alloys and need not be described in detail herein, as the variations in temperature will be readily understood by those skilled in the art. It will be understood of course that the temperature reached during the formation of an alloy, according to the invention, will vary with the percentages of the metals forming the alloy. In the case of eutectic alloys the temperatures will be lower than in cases where the percentages vary from that of the eutectic alloy.

As far as I am aware copper, nickel and silver are the only metals which may be alloyed with metals of the titanium group in the manner specified. Each have an amnity for the metals of the titanium group and, in the presence of hydrogen sweeping from the titanium metals, form eutectic alloys which fiow over the surfaces V of the particles of the titanium metals and protect the latter against contamination so that, as the temperatures are raised, they may diffuse through the particles of the titanium metals and form the final alloy.

In accordance with the patent statutes I have described my process with great particularity, but as to whether or not the principles described by me are the exact scientific principles involved I do not commit myself. Sufllce it to say that in an atmosphere of nascent hydrogen sweeping from the titanium metals copper, nickel and sil ver readily alloy withmetals of the titanium group below their melting points in the manner specififi herein.

While I have illustrated my method of production of alloys by describing the preparation of copper titanium alloys specifically, it will be obvious to those skilled in the art that the invention is not limited to any of the specific alloys described but is susceptible to variation and modification without departing from the spirit thereof and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. The method of forming alloys of a metal selected from a first group consisting of copper, nickel and silver and a metal selected from a second group consisting of the metals of the titanium sub-group of the fourth group of the periodic table of elements, which comprises mixing a powdered metal from the-first group with powdered hydride of a metal of the second group, raising the temperature of the mixture until the hydride dissociates into a metal and hydrogen, and further raising the temperature until the metal of the first group forms a fused alloy with the metal liberated from the hydride.

2. The method of forming alloys of a metal selected from a first group consisting of copper, nickel and silver and a metal selectedfrom a second group consisting of the metals of the titanium sub-group of the fourth group of the periodic table of elements, which comprises mixing a powdered metal from the first group with a powdered hydride of a metal of the second group, placing the mixture in a closed container, establishing a vacuum in said container, raising the temperature until the hydride dissociates into a metal and hydrogen, evacuating the produced hydrogen, and further raising the temperature until the metal of the first group forms a fused alloy with the metal liberated from the hydride.

3. The method of forming alloys of a metal selected from a first group consisting of copper, nickel and silver and a metal selected from a second group consisting of the metals of the titanium sub-group of the fourth group of the periodic table ofelements, which comprises mixing a powdered metal from the first group with a powdered metal of the second group containing occluded hydrogen, placing the mixture in a closed container, establishing a vacuum in the container, raising the temperature until the hydrogen evolves from the metal of the second group, evacuating the hydrogen, and further raising the temperature until the metal of the first group forms a fused alloy with the metal of the second group.

4. A method of production of alloys of copper and a metal of the titanium sub-group of the fourth group of the periodic table of elements comprising mixing powdered copper and the powdered hydride of the said metal, raising the temperature until the hydride dissociates into a metal and hydrogen, and further raising the temperatureuntil the copper forms a fused alloy with the metal liberated from the.hydride.

5. A method of production of alloys of copper and a metal of the titanium sub-group of the fourth group of the periodic table of elements comprising mixing powdered copper and the powdered hydride of the said metal, placing the mixture in a closed container, establishing a vacuum in said container, raising the temperature until the hydride dissociates into a metal and hydrogen, evacuating the produced hydrogen, and further raising the temperature until the copper forms a fused alloy with the metal liberated from the hydride.

6. A method of production of alloys of copper and a metal of the titanium sub-group of the fourth group of the periodic table of elements comprising mixing powdered copper and a metal of the said titanium group containing occluded hydrogen in a closed container, establishing a vacuum in said containenraising the temperature until the hydrogen evolves from the said metal, evacuating the hydrogen, and further raising the temperature until the copper forms a fused alloy with the said metal.

7. A method of production of alloys of copper and titanium comprising mixing powdered copper and titanium hydride, raising the temperature until the titanium hydride dissociates, and further raising the temperature until the copper forms a fused alloy with the titanium liberated from the hydride.

8. A method of production of alloys of copper and titanium comprising mixing powdered copper and titanium hydride, placing the mixture in a closed container, establishing a vacuum in said container, raising the temperature until the titanium hydride dissociates, evacuating hydrogen, and further raising the temperature until the copper forms a fused alloy with the titanium liberated from the hydride.

9. A method of production of alloys of cop- .per and titanium comprising mixing powdered copper and titanium containing occluded hydrogen, placing the mixture in a closed container, establishing a. vacuum in said'container, raising the temperature until the titanium containing hydrogen dissociates, evacuating hydrogen, and further raising the temperature until the copper forms a fused alloy with the titanium.

10. A method of production of alloys of copper and zirconium comprising mixing powdered copper and zirconium hydride, placing the mixture in a closed container, establishing a vacuum in said container, raising the temperature until the zirconium hydride dissociates, evacuating hydrogen, and further raising the temperature until the copper forms a fused alloy with the zirconium liberated from the hydride.

l1. A method of production of alloys of copper and zirconium comprising mixed powdered copper and zirconium containing occluded hydrogen, placing the mixture in a closed container, establishing a vacuum in said container, raising the temperature until the zirconium containing hydrogen dissociates, evacuating hydrogen, and further raising the temperature until the copper forms a fused alloy with the zirconium.

12. A method of production of alloys of copper and a metal of the titanium sub-group of the fourth group of the periodic table of elements comprising mixing powdered copper and a hydride of the said metal, placing the mixture in a container, establishing a vacuum in said container, raising the temperature until the hydride dissociates, evacuating the hydrogen, further raising the temperature above 700 C. but below the melting point of copper and continuing the heat treatment at that temperature until the copper reacts with said metal forming a fused alloy.

13. A method of production of alloys of pper and titanium comprising mixing powdered copper and-a hydride of the titanium, placing the mixture in a container, establishing a vacuum in said container, raising the temperature until the hydride dissociates, evacuating the hydrogen, further raising the temperature above 100 C. but below the melting point of copper and continuing the heat treatment at that temperature until the copper diffuses into the titanium forming a fused alloy.

'14. A method of production of alloys of copper and a metal of the titanium sub-group of the fourth group of the periodic table ofelements comprising mixing powdered copper and a hydride of the'said metal, placing .the mixture in a container, establishing a vacuum in said container, raising the temperature to a point not exceeding 1075" C., and continuing the heat treatment at that temperature until the copper reacts with said metal forming an intermetallic compound with said metal.

15. The method of forming alloys of a metal selected from a first group consisting of copper, nickel and silver and a metal selected from a second group consistingof the metals of the titanium sub-group of the fourth group of the periodic table of elements, which comprises mixing finely divided particles of the metal of the first group with finely divided particles of the metal of the second group containing heatevolvable hydrogen, the metals forming eutectic alloys at the points of contacts of the particles, raising the temperature of the mixture until the hydrogen evolves from the metal of the second group and the surfaces of the particles of the titanium group metal are completely wetted by the metal of the first group, and then further raising the temperature until the metal of the first group. diffuses into the metal of the second 8 0.

16. The method of production of alloys of a metal selected from a first group consisting of copper, nickel and silver and a metal selected from a second group consisting of the metals of the titanium sub-group of the fourth group of the periodic table of elements, which comprises mixing a powdered metal selected from the first group and a powdered metal selected from the second group and containing heat evolvable hydrogen therein, raising the temperature of the mixture until the hydrogen evolves from the metal and further raising the temperature until the metal of the first group forms a fused alloy with the metal of. the second group.

PETER P. ALEXANDER.