Specialized metallurgical processes – compositions for use therei – Processes – Producing or purifying free metal powder or producing or...
Patent
1991-08-19
1994-07-12
Wyszomierski, George
Specialized metallurgical processes, compositions for use therei
Processes
Producing or purifying free metal powder or producing or...
75354, C22C 104
Patent
active
053285018
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the production of metals, alloys and ceramic materials. More specifically, the invention is concerned with the mechanically activated chemical reduction of reducible metal compound(s) to produce metals, alloys or ceramic materials.
Most metallic elements occur in nature as oxides sulphides or phosphates in ore bodies. The refining process generally involves separation of pure oxides, sulphides and/or phosphates from the ore, and one or more reduction processes to convert the oxide, sulphide and/or phosphate to pure metal.
While the reduction process is specific to the particular element being refined, it usually involves either a chemical reaction, where the oxide, sulphide and/or phosphate is reduced by a second, more electro-positive element, or an electrochemical reaction driven by an electrical potential. Chemical reduction processes frequently require high temperatures, with one or more of the reactants being in the gas or liquid phase, so that sufficiently high reaction rates can be achieved.
In most conventional processes, pure metals are produced which are then mixed with other metals to form alloys using various melting and casting techniques. In some instances, where the production of alloys from pure metals is technically difficult or costly, it is possible to design chemical reduction processes which start with an appropriate mixture of metal oxides. The oxide mixture is directly reduced in a single step to the desired alloy composition by the addition of an appropriate reducing agent and high temperatures. Such processes include the reduction diffusion process and the co-reduction process used in the production of rare earth magnets. These processes use calcium as the reducing agent and involve heating to temperatures of above 1000.degree. C.
An alternative process to the production of alloys by melting their pure constituents is known as mechanical alloying. Mechanical alloying enables the production of alloys from powders of the pure constituents without the need for melting or high temperatures. The mechanical alloying process may be carried out in a high energy ball mill. The milling action causes repeated fracture and cold welding of the powder particles during ball-powder-ball and ball-powder-container collisions. The alloying process takes place as an inter-diffusion reaction across atomically clean surfaces joined by cold welding. Given sufficient time, the mechanical alloying process can produce a true alloy at the atomic level. It has been shown that it is possible to prepare certain alloys by the mechanical alloying process which were otherwise impossible to prepare by conventional means. It has also been shown that mechanical alloying can be used to produce amorphous alloys, particularly when the elemental powders exhibit a large positive heat of reaction, as well as intermetallic compounds and dispersion hardened alloys.
The present invention is concerned with a new chemical reduction process termed "mechanically activated chemical reduction" for manufacturing metals or alloys from reducible metal compound(s). The mechanically activated chemical reduction process is essentially an adapation of the mechanical alloying process. During the mechanically activated chemical reduction, chemical reduction reactions are caused to occur, as a consequence of the mechanical action, which results in the reduction of the metal compound(s) to the metal or alloy.
The mechanically activated chemical reduction process of the present invention also extends to the production of ceramic materials, that is, materials which contain one or more phases that are compounds of metals and non-metals. Thus, the process is capable of producing products which range from pure metals and their alloys with other metals or metalloids through to ceramic materials, which may also include metals and/or metalloids in their composition.
According to the present invention there is provided a process for the production of a metal, alloy or ceramic material, characterised in that:
a m
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McCormick Paul G.
Schaffer Graham B.
The University of Western Australia
Wyszomierski George
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