Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1992-01-23
1993-10-26
Wasil, Daniel D.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75232, 75236, 75244, 75245, 75246, 75249, 419 67, C22C 2900
Patent
active
052561836
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to reinforced composite materials and more particularly to a process for the provision of composite alloys reinforced by dispersed particles and the product thereof.
It is known that in order to improve the mechanical properties of metals it is possible to reinforce a metallic matrix with filaments or particles having high characteristics which are insoluble in the base metal. Reinforcing an alloy with ceramic particles, whiskers or fibres yields a material combining the most useful properties of both the metal and the ceramics. The nature and amount of the dispersed particles enable the obtained composite alloys to be adapted to different advanced technical requirements changing besides the mechanical also the physical properties such as thermal expansion, conductivity, magnetic properties etc. of the original alloy.
Such composite alloys can be obtained e.g. by mixing of granulated base metal and reinforcing particles followed by an extrusion process. The resulting materials are, however, liable to several defects like residual porosity and poor homogenity, and consequently a considerable reduction in ductility characterizes such extrusions is experienced.
Furthermore, this powder metallurgy route of manufacturing composites is rather expensive.
Another process, nowadays widely applied for obtaining composite alloys, is based on melting of a base metal and dispersing of particles in a metal matrix in the liquid phase. An intimate mixture of the particles and the molten metal can be obtained using this process. However, it is difficult to avoid sedimentation and segregation phenomena so that the resulting cast composite material may exhibit considerable variations in the desired homogenity, e.g. between the periphery and the interior of a cast block. Furthermore, it has been found that in case of some low ductility alloys the addition of ceramic particles does not result in any significant higher strength in gravity cast specimens.
It is of course possible to use whiskers or continuous fibres as reinforcing means in order to achieve appreciable improvements of the composite characteristics. However, the production costs will also increase so significantly that this is not a real alternative to choose for most applications.
It is therefore the object of the present invention to provide a novel composite material, particularly a metal or metal alloy, reinforced by particles insoluble in the metal matrix and dispersed in a manner resulting in substantially improved characteristics, especially high strength and good ductility of the composite alloys.
The present invention is embodied in a process for preparing a composite material by incorporating particulate non-metallic reinforcement into a molten matrix material followed by a rapid solidification providing an intermediate granulated composite alloy material, mixing of the obtained composite alloy granules with granules of host metal and finally compaction and extruding of the resulting mixture.
The base metal can, for example, be aluminium, magnesium, copper, nickel, titanium or their alloys. As particulate additions particles formed of refractory compounds having high elasticity modulus may be used, such as metal oxides, carbides, silicides or nitrides.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be readily understood and described in more details by means of the following example(s) and by reference to the accompanying drawings, FIGS. 1-6, where
FIG. 1 illustrates graphically the ultimate strength and yield strength of the extruded materials with and without reinforcing particles,
FIG. 2 illustrates the tensile properties of the extrusions at room and elevated temperatures,
FIG. 3 shows in a cross-sectional longitudinal view a photo of the extruded reinforced composite alloy material macrostructure (magnification 13,6),
FIG. 4 shows the macrostructure from FIG. 3 at higher magnification (50.times.),
FIG. 5 illustrates the distribution pattern of the reinforcing particles taken at the plan perpendicular to
REFERENCES:
patent: 4756754 (1988-07-01), SinghDeo
patent: 4915903 (1990-04-01), Brupbacher et al.
patent: 4916029 (1990-04-01), Nagle et al.
patent: 4916030 (1990-04-01), Christodoulou et al.
Auran Lars
Ruch Wolfgang W.
Ryum Nils
Mai Ngoclan T.
Norsk Hydro a.s.
Wasil Daniel D.
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