CA2007796A1 - Fabrication of creep-resistant specialty alloys reinforced with ferroaluminum shots - Google Patents

Abstract

Abstract The fusible alloys or zinc-based alloys are reinforced with ferroaluminum shots to improve the creep resistance of parts used for fire sprinklers, thermal plugs of valves or cylinders, bearings, gears, brackets, fasteners, seals, bushings, rollers, axle housings, cams, guides, lost core plastic molding, inserts, work holding, etc. Other reinforcible matrix alloys include tin-based, lead-based, copper-based, and aluminum-based alloys used for dynamic and structural parts requiring strength and creep resistance. Ferroaluminum shots are comprised primarily of iron and aluminum and they are light, relatively nonreactive with zinc, and bondable to afore-mentioned matrix alloys by using inorganic acid-based fluxes of zinc chloride, ammonium chloride, a mixture of chlorides, or a mixture of chlorides and fluorides.
Other fluxes such as organic acid-based chemicals work as a cleaning agent when they can clean surface oxides of both the matrix alloy and reinforcing shots. Materials for alternative reinforcement include conventional steel or iron shots coated with sodium nitrite, ferroaluminum shots coated with sodium nitrite, nickel, copper, monel, refractory metals, copper or nickel-coated metals, copper or nickel-coated plastics, and copper or nickel-coated ceramics.

Description

: Z C~ 7 7 ~i Background of the Invention The die casting industry has tried in the past to produce strong parts using fiber- or particle-reinforced alloys. The result was unsuccessful because of the difficulty of melt-flow, i.e.,;fibers and particles do not flow intrinsically and hence die cast parts show very rough surface texture, voids, cracks, and restricted flow in thin sections. The irregular geometry of particles or fibers with sharp edges, corners, and protrusions induces poor melt-flowability by the mechanism of interlocking and agglomeration. In other words, they are not die-castable and thus parts with a smooth surface finish without defects cannot be produced , for example, when the content of particles is greater than about 5 ~ by volume. The breakthrough for this problem has been achieved by the present invention, i.e., shot-reinforced fusible, tin-based, lead-based, or zinc-based alloys.
Shots arè different from particles or fibers owing ta their spherical shape and they intrinsically flow very well up to about 45 ~ by volume, producing a very smooth surface without voids in die casting. Therefore, the mass production of die cast parts which are strong and creep-resistant has become poss~ible with shot-reinforced alloys.
Shots, in short, serve thw following pueposes.
(1) Strengthening (2) Flowability (3) Die-castability Fibers or particles serve only the strengthening purpose with no `

flowability. In lost core technology, for instance, the inside surface of intake manifolds must be smooth for the increase of engine efficiency. When the plastic is molded around the fusible core and subsequent decoring is done, the inside surface of the plastic manifold is smooth only when the cast core surface is smooth. Such smooth core having a desiable strength can be made only with shot-reinforced alloys.
As a practical example, fusible alloys used in a fire sprinkler system have a problem of cold flow under a stress due to the weak strength of fusible alloys. In a prior art described in U.S. Pat. No. 3,605,902, the reinforcement with random length loose fibers has been suggested for strengthening fusible alloys.
This idea, howevçr, has not been successfully reduced to practice because of the difficulty of economically forming an intermetallic bonding between fibers and matrix alloy.
An extrusional flow of a fusible alloy under a high gas pressure when it is used in a thermal plug of a valve or cylinder has been a problem and a composite alloy comprised of conventional fusible alloy reinforced with steel shots has been presented as a solution in the patent-pending invention of U.S. File No.
07,290,743 filed Dec. 27, 1988.
The creep problem of zinc-based alloys has also been solved by reinforcing zinc alloys with steel shots as described in the patent-pending invention of U.S. File No. 07,314,950 flled Feb.
23, 1989.
In the preceding two examples, the bonding between steel shots and matrix alloys was accomplished by using a flux of ammonium chloride. Previously an inert or reducing atmosphere was employed to induce bonding between the alloy matrix and fibers coated with bondable metals such as copper, In an air atmosphere such intermetallic bonding is not achieved~due to tlhe oxidabion problem. The use of flux enables the bonding to be achieved in air without the presence of bondable coating layer. Another uniqueness of the fluxing method is that the flux is applied to the molten liquid metal, not to the solid metal as has been done in the past. The appropriate flux must clean surface oxides of both the liquid alloy and reinforcing shots, thereafter forming an instantaneous intermetallic bonding between the molten alloy and shots. The uniqueness of flux in the present invention is thus as follows.
(1) Surface oxides of both the molten alloy and steel shots are cleaned by the flux in an air atmosphere.
(2) The fluidity of the molten liquid-state alloy covered with a liquid flux layer provides the high mobility required to wet the large number of shots in a very short time period.
(3) Immediately after surface oxides are removed, instantaneous intermetallic bonding is achieved betveen shots and liquid alloy.

(4) The presence of a protective flux layer on the molten alloy surface negates the requirement of an inert or reducing atmosphere for mixing. The air environment is just enough for mixing with the aid of a flux.

,:

~ .
: .

Generally, there are various kinds of fluxes: inorganic acid fluxes, orqanic acid fluxes, and liquid rosin fluxes. In the present invention, alternative acid fluxes will be introduced to induce the wetting and ferroaluminum shots which are comprised primarily of iron and aluminum will~be employed as reihforcement.
The advantages of ferroaluminum shots over conventional steel shots are as follows. For certain applications such as lost core plastic molding, it is desirable to reduce the weight of steel shots for ease of handling and for reduction of energy consumption. The handling problem becomes serious particularly when the part made of fusible alloy is large. Such heavy product is handled by a robot and very often, the clamping pressure of a robotic arm induces indentation marks on the hot cast product surface, rendering the cast surface damaged. In another example involving zinc-based alloys, the reactivity of zinc with steel is very high to form a solid cake and thus the suppression of such reactivity is required to maintain the good melt-flow property. The preceding problems can be solved by ferroaluminum shots since iron-aluminum alloy shots are lighter than steel shots and the reactivity is decreased by the presence of aluminum in shots.
The problem of reactivity of zinc with steel or iron can be overcome by satisfying the following two conditions. Firstly, the aluminum content in the zinc alloy must be high enough to reduce the reaction rate between zinc and iron. Secondly and more importantly, the temperature of the molten zinc alloy must be low enough to suppress the reaction between zinc and iron.
Both conditions are met by ferroaluminum shots when the molten bath temperature is lower than about 850 degree F. Alternatively, conventional steel shots can be mixed wlth zinc and then aluminum is added quickly to stop the r~eaction ("melt-freeze" method) or steel shots are mixed directly with zinc-aluminum alloy using an acid flux comprised of chlorides and fluorides ("fluxing" method).
Generally the fluxing and "ferroaluminum" method are more compatible with the conventional die casting process than the melt-freeze method.
The kinds of metal matrix reinforcible with ferroaluminum shots include not only zinc-based alloys but also tin-based, lead-based, bismuth-based, copper-based, and aluminum-based alloys. They can be used as gears, bearings, seals, bushings, rollers, cams, guides, brackets, axle housings, fasteners, knobs, inserts, housings, fusible links for fire sprinklers, thermal plugs for valves or cylinders, cores for lost core plastic molding, for work holding and work supporting, for accurate mold cold work, for setting punches in press tools, for tube bending, in die forming and jewellery manufacture, for proof casting and lens blocking, for protective blocks for radiography, and any static and dynamic parts requiring strength and creep resistance using afore-mentioned alloys. The strength of such alloys reinforced with shots is increased to help resist the creep or cold flow tendency and the flowability is provided by spherical shots.

, Su~mary of the Invention Zinc-based, tin-based, bismuth-based, lead-based, copper-based, aluminum-based, and any low-melting fusible alloys used for structural and dynamic parts are wetted,by ferroaluminum shots using inorganic acid fluxes such as zinc chloride, ammonium chloride, a mixture of chlorides, or a mixture of chlorides and fluorides. Other organic acid fluxes containing ammonium fluobo-rate wor~ when they clean surface oxides of both matrix alloys and shots. All the afore-mentioned alloys are wetted effectively by ~
steel or iron shots coated with sodium nitrite by using a chloride based flux. Other shots wettable with the preceding alloys~by using an acid-based flux include stainless steel, copper, nickel, V
monel, refractory metals, copper or nickel-coated steel, any copper or nickel-coated ceramics, any nickel or copper-coated plastics, any copper or nickel-coated metals, and any strong materials coated with bondable metallic layers such as those listed above.
As reinforcement for zinc alloys, the content of aluminum in ferroaluminum must be greater than a minimum in order to decrease the reaction rate between iron and zinc to a negligible level.
The shot-reinforced alloys are then die-castable with the surface smoothness comparable with the conventional unreinforced alloys while improving the creep or cold flow behavior.
~ rass die casting alloys are also reinforcible with shots to improve the creep behavior. Magnesium-based alloys require a special flux under a nonoxidizing atmosphere for shots to be mixed.

Brief Description of Drawings Fig.1 is a schematic illustration of a fusible thermal plug comprised of two layers: one layer consists of matrix alloy and the other layer consists of reinforcing shots embedded in the matrix phase.
Fig.2 is a schematic illustration of a fusible alloy used in a fire sprinkler system.

Detailed Description of the Invention Iron-aluminum shots are fabricated by injecting a high pressure water jet to the molten iron-aluminum alloy stream and quenching into a water tan~. Shots contain other miscellaneous impurity elements such as carbon, manganese , silicon, sulfur, and phosphorous. Shots areicoated with sodium nitrite to prevent them from environmental corrosion and also to help assist the bonding reaction. The molten iron-aluminum bath is prepared by adding aluminum or ferroaluminum to the steel bath and the size of shots is controlled by adjusting various parameters such as shooting angle, melt temperature, water jet pressure, diameter of water jet, size of molten alloy stream, etc.
Ferroaluminum shots become bondable to the tin-based, bismuth-based, lead-based, copper-based, zinc-based, and aluminum-based alloyg by adding cleaning chemicals of zinc chloride, ammonium chloride, a mixture of zinc chloride and ammonium chloride, and a mixtuxe of chlorides and fluorides. For aluminum-based alloys and zinc-based alloys containing aluminum, a mixture of zinc chloride, ammonium chloride, and sodium fluoride is used as a flux.
Reinforcible alloys are not limited to the afore-mentioned alloys but to any alloys whose melting point is lower than that of iron-aluminum alloy shot and wettable by the alloy shots by means of appropriate cleaning agent of flux. For example, magnesium-based alloys containing aluminum can be reinforced with ferroaluminum shots using a mixture of chlorides and fluorides as a flux under .
~; . , ,:.
.
~': . , :

.
~,..: ,--\

a protective atmosphere. In priciple, an appropriate cleaning agent must clean (or remove surface oxides of) both the alloy shot and matrix alloy in order to induce the intermetallic bonding between them. Chloride-based acid fluxes are such cleaning agents as exemplified in ammonium chloridet zinc chloride, etc. Other inorganic acid or organic acid fluxes can work when they clean surface oxides of both the matrix alloy and ferroaluminum shots.
Organic acids contain ammonium fluoborate as an ingredient.
The spherical shot geometry is the best shape in terms of good melt-flow property and surface smoothness of a die cast product.
Other shapes such as particles, aggregates, or short fibers may be applicable as reinforcement, but they easily produce voids, cracks, rough surfaces, restricted flow in thin-sections, and blocking of gates owing to the poor melt-flowability. Hybrid composites in which various kinds of reinforcement are incorporated ~imultaneously utilize some or all of shots, particles, aggregates, or short fibers as reinforcing agents. It is possible to maintain the melt-flowability when the reinforcing agents consist of mostly shots and a very small amount of particles or/and fibers.
As the strength increases with the increase of shot amount, the amount of shots must be greater than a minimum for a desirable strength improvement. However, as the content of shots rises, the melt-flow behavior starts to deteriorate and hence the amount of shots must be less than a maximum ~o maintain the good melt-flow property. The precise magnitude of such minimum and maximum depends on the shot size, kinds of matrix phase, kinds of shot - : :
'.: ' ' ,' ' . ~ '' . :
-,: , ' , . .. .. . . . .
, i , , ~ .: . ~ . , ~' material, and other process parameters.

The size of shots is determined by two factors: geometrical complexity of a desired product and strength requirement. The more complex the shape geometry, the finer the shot size and the finer the shot diameter, the stronger the mechanical strength.
However, as the shot size decreases, the flow behavior tends to deteriorate and thus the maximum mixable content of shots tends to decrease. Consequently, there is an optimum condition in terms of shot amount, shot size, strength requirement, and flow behavior for a specific application. Generally, the diameter of shots ranges from about 0.004 to 0.2 inch and when the size of shot is much finer than the lower limit of 0.004 inch, the flow behavior deteriorates rapidly as in the case of pPwder reinforcement so that it is not die-castable.
Ferroaluminum shots are not the only kind of bondable reinforcement to the afore-mentioned matrix alloys but also conventional steel or iron shots coated with sodium nitrite and sodium nitrite-coated ferroaluminum shots are bondable to the matrix alloy. Other bondable reinforcements include stainless steel, copper, nickel, cobalt, monel, refractory metals, copper-coated steel, nickel-coated steel, copper or nickel-coated ceramics , copper or nickel-coated plastics, copper or nickel-coated metals, and any strong materials coated with bondable metallic layers comprised primarily of copper or nickel. They are insoluble in but wet by the preceding matrix alloys. The preceding reinforcements generally require the presence of a flux for bonding.

~o~6 However, the bonding can take place without the presence of a cleaning flux when the mixing process is performed under a nonoxidizing (inert or reducing) environment and when reinforcing shots are coated with copper or nickel which are bondable to the matrix alloy. ~Conventional steel~or iron shots are mixed with the afore-mentioned matrix alloys by using the flux of zinc chloride or a mixture of zinc chloride or ammonium chloride. All the preceding shots coated with sodium nitrite are also bondable to the afore-mentioned alloys by using the chloride-based fluxes.
The function of sodium nitrite is twofold. It acts as a rust inhibitor and also acts with chloride to generate a mixture of nitric and hydrochloric acid so that the surface oxides can be rapidly removed.
The advantages of ferroaluminum shots are light weight, easy handling, energy saving, reduced reactivity with the matrix alloy ~particularly with zinc), and improved resistance to the environmental corrosion.
For zinc alloys, the content of aluminum in ferroaluminum must be greater than a minimum to suppress the reaction between zinc and iron. When zinc chloride or ammonium chloride is used as a flux, the iron-25 wt.~ aluminum alloy shot is mixable but the ferroaluminum shot containing 75 wt.% aluminum is not mixable and therefore, for high aluminum content shots, aluminum soldering fluxes consisting of chlorides and fluorides are required.
Tin~based alloys are comprised primarily of tin and some or all elements of lead, bismuth, antimony, cadmium, indium, and silver.

-- 2~C~779~

Lead-based alloys are comprised primarily of lead and some or all elements of tin, bismuth, antimony, cadmium, indium, and silver.
Bismuth-based alloys are comprised primarily of bismuth and some or all elements of tin, lead, antimony, cadmium, indium, and silver. They are wettable with ferroaluminum or sodium nitriter coated iron or st!eel shots using chloride-based fluxes such as zinc chloride or ammonium chloride. For high aluminum content ferroaluminum shots, aluminum soldering flux is employed. Using aluminum fluxes, aluminum shots can be used as reinforcement for lost core molding cores.
Zinc-based alloys are comprised of a major element of zinc and a minor element of aluminurn together with copper and magnesium and a trace amount of some or all elements of iron,lead, cadmium, tin, titanium, nickel, and chromium. They are mixable with sodium nitrite-coated iron or steel shots or ferroaluminum shots using acid fluxes consisting of ammonium chloride, zinc chloride, and sodium fluoride at temperatures lower than about 830 to 850 degree F but higher than the melting points of zinc alloys and also the working temperat~re of fluxes. For example, the melting point of zinc plus 3.5 - 4.3 wt.% aluminum alloy ranges from 718 to 727 degree F.
Copper-based alloys are comprised primarily of copper and some or all elements of zinc, tin, lead, iron, alurninum, manganese, and silicon. Aluminum-based alloys are comprised primarily of aluminum and some or all elements of tin, silicon, iron, copper, and nickel. They are wetted with ferroaluminum or steel shots .

. . .

coated with sodium nitrite using chloride-based fluxes.
Magnesium-based alloys are comprised of a major element of magnesium and a minor element of aluminum together with a trace amount of zinc, silicon, manganese, and copper. Shots are mixed under an inert atmosphere usingia special flux consisting of magnesium chloride and other chlorides. Applications include wheels , transmission housings, crank cases~ chain saws, lawn mower decks, tools, etc.
One example of organic acid-based flux is comprised of aminoehtylethanolamine, ammonium fluoborate, and zinc oxide.
For ferroaluminum shots or conventional iron or steel shots, a chloride-based eutectic flux comprised of potassium chloride and zinc chloride is a good cleaning agent especially for zinc alloys since it produces no toxic gases.
Alternative shots for reinforcement are steel, iron, chromium, and titanium. Another alternative shots are alloys based on iron, steel, nickel, cobalt, chromium, titanium, aluminum, copper, or refractory metals, which are bondable to the afore-mentioned matrix alloys by using a chloride-based flux. For example, iron-based alloys comprised of iron and carbon and a tiny amount of silicon or magnesium àre bondable to the matrix alloy by employing a chloride -based flux. In short, any strong metal shots comprised of one or more metallic elements can be used as reinforcement when they become bondable by means of a flux.
For zinc alloys, the density of cast iron shots is controlled to be about equal to the specific gravity of matrix alloy by 2~ t~7s~

adjusting the carbon content such that the iron shots can be dispersed homogeneously. The reactivity of iron shots wi.th zinc is also reduced by increasing the carbon content~ The density of ferroaluminum shots can also be controlled by adjusting the aluminum content. The aluminum content in ferroaluminum shots varies depending on specific applications but generally it ranges from 0.1 to 99 weight ~.

2~ 796 Thermal Pluq Application When the density of reinforcing steel, iron, or ferroaluminum shots is different from that of the matrix phase alloy, two slightly ~ifferent~layers are formed in the cavity hole of a thermal plug filled with a fusible alloy as illustratèd in Fig.;1.
The degree of morphological contrast depends on the filling method and if rapidl~ solidified, uniform morphology can be obtained.
The dense layer 2 provides the extra strength to resist the extrusional flow under a high gas pressure and the loose layer 1 seals the plug additionally to prevent any gas leakage. When the fusible alloys are reinforced with particles or short fibers, the gas leakage tends to occur owing to the poor flowa~ility-induced voids or/and cracks. Cracks often occur from the torque applied to tighten the plug.
As a fusible thermal plug for natural gas cylinders, medical ga~ cylinders, acetylene aylinders, carbon dioxide cylinders, or any gas cylinders or their valves, matrix alloys fusible at about 212 ~r 165 degree F are mixed with steel or ferroaluminum shots and filled into the plug cavity using appropriate fluxes. Such plugs resist the extrusional flow at 130 degree F under a gas pressure of about 3600 psi for at least 24 hours with the alloy fusing at about 212 degree F, for example. The improved creep strength without any extrusional flow enables the installation of a thermal plug in conjunction with pressure-sensitive rupture disc in a pressure gas cylinder valve such as carbon dioxide ' ' 2Q~ 96 aluminum cylinder to safeguard the safety against temperature as well as pressure. Accordingly, a fatal catastrophe which happens when the rupture disc blocks the release of pressurized gas in a cylinder can be prevented. Partially filled aluminum cylinders are particularly dangerous when only the pressure-sensiti;ve rupture disc is available for safety. The availability of temperature-sensitive thermal plug in addition to pressure-sensitive rupture disc will guarantee the safety against both the pressure and temperature independently. ~
Small amount`of particles or fibers can be added when they do not degrade the f1owabi1ity.

, --1, ,.. ...... . .

:-' ";: : , '~

' ' ,. . ,:
.
' 2`~ 36 Fire Sprinklers For use as fusible links of fire sprinklers, the melting point of fusible alloys varies according to the requirements of a specific application'and generally the fusing temperature is less than about 600 degree F. As the strength of new creep-resistant alloys is higher than conventional fusible alloys, the mass or dimension of fusible links in a sprinkler system can be reduced to decrease the response time in case of fire. The increase of creep strength also eliminates the problem of premature failure of a sprinkler system since the fusible link is under a continuous load until it melts due to fire. As shown in Fig.2, the new alloy consists of conventional matri:~
1 reinforced with steel or ferroalumnum shots 2.
Small amount of particles or fibers can be added when they do not degrade the flowability.

., .. . . .

, ;~6 Die Cast Zinc AlloYs The reactivity of iron with zinc is significantly reduced when the aluminum content in the melt is greater than about 3 wt.
% and accordingly, ferroaluminum shots having the aluminum content greater than about 3 wt.~ are mixed with conventional zinc alloys such as number 3, number 5, number 7, number 16, ZA 8, and ZA 12.
Since the strength comes from strong shots, the cheap hot chamber process may be applicable for the whole range of zinc alloys when the processing temperature is lower than about 830 to 850 degree F.
The maximum amount of shots without degrading the flowability is about 30 to 40 wt.% and depending on the kinds of zinc alloy matrix , a range of strengths can be obtained.
Alternatively, conventional zinc aluminum alloys are mixable with conventional steel or iron shots by using a flux comprised of zinc chloride, ammonium chloride, and sodium fluoride at about 780 to 820 degree F. A crude method of manufacturing shot-reinforced zinc alloys is-to coat steel skots with the zinc layer and then add the 2inc-coated shots to the zinc-aluminum melt in such a way that the total aluminum content in the melt is greater than about 3 wt.~ to suppress the reaction of zinc with iron. -Generally, steel or ferroaluminum shots can be mixed with thezinc-based matrix alloys by employing any fluxes that become active below about 850 degree F but above the melting temperature of zinc alloys and also that can effectively remove surface oxides of both shots and matrix phase alloy. The melting point o~ zinc alloys ranges from 710 to 910 degree F. For example, zinc plus 3.~-4.3 wt.~ aluminum alloy melts at 718 to 727 degree F and zinc plus 25-28 wt.~ aluminum alloy melts at 707 to 909 degree F.
Regardless of the kinds of zinc alloy, the processing temperature must be less than about 830 to 850 degree F in order for iron, steel, or ferroaluminum shots to be mixed without undesirable reaction between zinc and iron.
Potential applications include any zinc alloy products used under a constant stress above room temperature, for bolting applications such as fasteners and brackets, and under the hood application in automobile or vehicles. The prospective zinc alloys must be processed below about 850 degree F and thus the number 3, number 5, number 8, number 16, ZA 8 and ZA 12 alloys are some of candidates to be reinforced with shots to improve the creep behavior and additionally to reduce the production cost.
For gravity casting, small amount of particles or fibers can be added when the melt-flowability is not degraded. Cast iron shots with high carbon content are bondable to zinc alIoys usinlg the eutectic flux comprised of potassium chloride and zinc chloride.
Zinc alloys contain a small amount of magnesium to improve the oxidation resistance and a small content of copper to enhance the strength.
Conventional iron shots bonded and immersed in the zinc-aluminum alloy melt can have a density close to that of the matrix alloy by adjusting the amount of minor elements such as carbon and aluminum.

~6 Lost Core Plastic Moldinq When tin-bismuth or tin-lead-antimony alloys are reinforced with ferroaluminum shots, the weight of die-cast cores is reduced due to the~aluminum content.~ The light weight of core eases the problem of handling and helps the decoring process by floating to the surface. Although ferroaluminum shots are lighter than tin based matrix alloys, the die casting process produces a self-turbulant flow for homogeneous mixing of shots in the matrix alloy for a uniform strengthening effect.
Sodium nitrite-coated steel, iron, or ferroaluminum shots become bondable to the tin-based or bismuth-based fusible alloys by using zinc chloride or a mixture of zinc chloride and ammonium chloride. Aluminum shots without any bondable metal coating such as copper are mixed directly with fusible alloys by using an aluminum flux comprised of ammonium chloride, zinc chloride, and sodium fluoride or by using an eutectid flux comprised of potassium chloride and zinc chloride~ Conventional steel or iron shots are bondable to tin or bismuth-based alloys by using a flux of ammonium chloridelor a mixture of zinc chloride and ammonium chloride. Small amount of particles or fibers can be added when they do not degrade the flowability.

37~

Example 1. Zinc Alloys Zinc-aluminum alloys are mixed with steel or iron shots using an acid flux comprised of ammonium chloride, zinc chloride, and sodium fluorlde. The zinc alloys are also mixable with ~ !
ferroaluminum shots using the same flux at about 800 degree F. The amount of shots is about 25 to 30 wt.% and the size of shots ranges from 0.004 to 0.1 inch in diameter. In order to maintain the melt temperature below about 850 degree F, the content of aluminum in zinc alloys is limited to below about 10 wt.%.
The kinds of zinc alloys mixable with shots are as follows:
(1) About 3.5-4.3 wt.% aluminum, about 0.25 wt.% copper, about 0.02-0.05 wt.% magnesium, and remainder zinc (number 3 alloy).
(2) About 3.5-4.3 wt.% aluminum, about 0.75-1.25 wt.% copper, about 0.03-0.08 wt.% magnesium, and remainder zinc (number 5 alloy).
(3) About 3.5-4.3 wt.% aluminum, about 0.25 wt.% copper, about 0.005-0.02 wt.~ magnesium, about 0.005-0.02 wt.% nickel, and remainder zinc (number 7 alloy).
(4) About 0.01-0.04 wt.% aluminum, about 1.0-1.5 wt.% copper, about 0.02 wt.% magnesium, about 0.15-0.25 wt.% titanium, about 0.1-0.2 wt.% chromium, and remainder zinc (number 16 alloy).
~5) About 8.0-8.8 wt.~ aluminum, about 0.8-1.3 wt.% copper, about 0.03-0.015 wt.% magnesium, and remainder zinc (ZA 8).
(6) About 10.5-11.5 wt.% aluminum, about 0.5-1.25 wt.% copper, about 0.015-0.03 wt.~ magnesium, and remainder zinc (ZA 12).

~a7~96 Example 2. Tin alloys Composite alloys comprised of tin-based matrix alloy reinforced with ferroaluminum shots~are fabricated by using a flux of zinc chloride. The content of shots is about 30 to 45 wt.% and the size of shots ranges from 0.004 to 0.1 inch in diameter. Some examples of the tin-based matrix phase are as follows.
(1) About 89 wt.% tin, about 7.5 wt.% antimony, and about 3.5 wt.%
copper.
(2) About 59 wt.% tin, about 38 wt.~ lead, and about 3 wt.%
antimony.
(3) About 10 wt.~ bismuth, and about 90 wt.% tin.
Sodium nitrite-coated steel shots are also mixed with tin alloys using ammonium chloride or zinc chloride with the shot content being about 30 to 45 wt.% of the composite alloy.

~r.~.7~.~

Example 3. Bismuth Alloys Composite alloys comprised of bismuth-based matrix alloy reinforced with ferroaluminum shots~are fabricated using a flux of zlnc chlorlde or a mixture of ammonium chloride and zinc chloride. The content of shots is about 30 to 45 wt.% of-the composite alloy and the size of shots ranges from 0.004 to 0.1 inch in diameter. Sodium nitrite-coated steel shots are also mixed with bismuth alloys using chloride-based fluxes. Some examples of matrix compositions are as follows.
(1) About 54 wt.~ bismuth, about 26 wt.% tin, and about 20 wt.
cadmium.
(2) About 50 wt.~ bismuth, about 27.8 wt.% lead, about 12.4 wt.
tin, and about 9.3 wt.% cadmium.
(3) About 57 wt.% bismuth, about 17 wt.% tin, and about 26 wt.%
indium.
~4~ About 57 wt.% bismuth, and about 43 wt.% tin.

Example 4. Copper Alloys Composites consisting of copper-based matrix alloy reinforced with ferroaluminu~ shots or sodium nitrite-coated steel shots are fabricated using a flux of ~inc chloride or a mixture of zinc chloride and ammonium chloride. The content of shots is about 20 to 30- wt.~ of the composite alloy and the size of shots ranges from 0.004 to 0.1 inch in diameter.
One example of matrix compositions is about 58-63 wt~ copper, about 1.0 wt.% tin, about 0.5-2.5 wt.% lead, about 0.5 wt.% iron, about 0.2-0.8 wt.% aluminum, about 0.5 wt.% manganese, and about 0.5 wt.% silicon.

2(~ '7~6 Example 5. Aluminum Alloys Composites comprised of aluminum-based alloy matrix reinforced with ferroaluminum shots are fabricated by using a flux consisting of ammonium chloride, zinc chloride, and sodium fluoride, or by a mixture of zinc chloride and ammonium chloride. Sodium nitrite-coated steel shots are also bondable using the preceding fluxes.
The content of shots is about 20 to 30 wt.% and the diameter of shots ranges fro~ 0.004 to 0.1 inch. The composition of aluminum alloy is, for example, about 80 wt.% aluminum, and about 20 wt.%
tin together with small additions of silicon, iron, copper, and nickel.

~Q~7~

Example 6. Lead Alloys Composites comprised of lead-based alloy matrix reinforced with steel shots, sodium nitrite-coated steel or iron shots, or ferroalumihum shots are fabricated using a flux consisting of a mixture of zinc chloride and ammonium chloride. The content of shots is about 30 to 40 wt.% of the composite alloy and the diameter of shots ranges from 0.004 to 0.1 inch. One example of lead alloy is about 83 wt.% lead, about 15 wt.% antimony, and about 1 wt. % tin.

7~

Example 7. Magnesium Alloys The matrix alloy is comprised of about 9.0-10.5 wt.~ aluminum, about 0.3-1.0 wt.% zinc, about 0.3 wt.% silicon, abouL 0.15-0.4 wt.% manganese, about 0.15 wt.~ copper, and remainder magnesium.
Steel or ferroaluminum shots are mixed with the magnesium alloy under an inert nitrogen atmosphere using a flux consisting of chlorides~and fluorides.

Although but seven embodiments of the present investigation have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be mad~ therein without departing from the spirit of the invention. , , (-

Claims (20)

1. A method of fabricating creep-resistant shot-reinforced alloys having a good melt-flowability, said matrix alloy is selected from the group consisting of zinc-based, tin-based, bismuth-based, lead-based, copper-based, aluminum-based, and magnesium-based alloys, said shots are mixed with said alloys by using an acid-based flux to form an intermetallic bonding.

2. The alloy of claim 1, wherein said shots are essentially a ferroaluminum alloy comprised primarily of iron and aluminum with the aluminum content less than about 99 weight %, steel or iron shots, or steel or iron shots coated with sodium nitrite.

3. The alloy of claim 1, wherein the geometry of shots is generally spherical without any sharp corners, edges, pits, or protrusions impeding the flow behavior.

4. The alloy of claim 1 wherein the content of said shots is greater than about 5 to 10 wt.% for strengthening and less than about 40 to 50 wt.% for a good melt-flow.

5. The alloy of claim 1, wherein said shots are made bondable to the said matrix alloy by using a flux selected from the following group:
(1) Inorganic acid fluxex including ammonium chloride, zinc, chloride, a mixture of chlorides, and a mixture of chlorides and fluorides.

(2) Organic acid-based fluxes containing ammonium fluoborate and aminoehtylethanolamine.

6. The alloy of claim 1, wherein the material of said shots include stainless steel, steel, iron, copper, nickel, titanium, chromium, silver, gold, monel, cobalt, refractory metals, their base alloys, any copper- or nickel-coated metals, any copper or nickel-coated plastics, any strong metals and alloys thereof which often have a bondable coating film if uncoated strong materials are not bondable with a flux, and any composite materials which are bondable to the said matrix alloys.

7. The alloy of claim 1, wherein the diameter of said shots ranges from about 0.004 to 0.2 inch.

8. The alloy of claim 1, wherein said ferroaluminum shots, steel or iron shots, or sodium nitrite-coated steel or iron shots become bondable to said zinc alloys by using a chloride-based flux consisting of zinc chloride, ammonium chloride, and sodium fluoride, an eutectic flux comprised of sodium chloride and zinc chloride, or acid fluxes which become active at a temperature lower than about 850 degree F
but higher than the matrix alloy melting point.

9. The alloy of claim 1, wherein said melt-flowable matrix alloy is any alloy that meets the following requirements:
(1) The melting point of the matrix alloy is lower than that of reinforcing shots.
(2) The matrix alloy is made bondable to shots by using a cleaning flux or by employing a nonoxidizing environment during mixing when the shots are coated with bondable metallic layers comprised primarily of copper.

10. The alloy of claim 1, wherein said shots for lost core plastic molding include conventional steel or iron shots, ferroaluminum shots, or any metal shots bondable to said tin-based or eutectic tin-bismuth fusible alloys by using a flux of ammonium chloride, zinc chloride, an eutectic mixture of potassium chloride and zinc chloride, or a mixture of chlorides or/and fluorides.

11. The alloy of claim 1, wherein said matrix alloys contain a major element of said shots and additionally small amount of short fibers or/and particles such that the flowability and surface smoothness of cast product is not degraded.

12. The alloy of claim 1, wherein tin-based alloy is comprised primarily of a major element of tin and some or all of bismuth, lead, cadmium, indium, antimony, silver, and copper.

13. The alloy of claim 1, wherein said zinc-based alloy is comprised primarily of a major element of zinc and some or all of aluminum, magnesium, copper, iron, lead, cadmium, tin, titanium, nickel, and chromium.

14. The alloy of claim 1, wherein said lead-based alloy is comprised primarily of a major element of lead and some or all of antimony, tin, and arsenic.

15. The alloy of claim 1, wherein said bismuth-based alloy is comprised primarily of a major element of bismuth and some or all of tin, lead, antimony, cadmium, indium, copper, and silver.

16. The alloy of claim 1, wherein said copper-based alloy is comprised primarily of a major element of copper and some or all of tin, lead, iron, aluminum, manganese, and silicon.

17. The alloy of claim 1, wherein said aluminum-based alloy is comprised primarily of a major element of aluminum and some or all of tin, silicon, iron, copper, and nickel.

18. The alloy of claim 1, wherein said magnesium-based alloy is comprised primarily of a major element of magnesium and some or all of aluminum, zinc, silicon, manganese, and copper.

19. The alloy of claim 1, wherein said zinc-based alloy contains iron shots having a density almost same as that of the matrix alloy by adjusting the content of minor elements of carbon and aluminum.

20. The alloy of claim 11, wherein the material of said fibers or particles include copper- or nickel-coated steel or iron, stainless steel, copper, nickel, titanium, chromium, silver, gold, monel, cobalt , refractory metals, their base alloys, any copper- or nickel-coated metals, any copper- or nickel-coated plastics, any strong metals and alloys thereof which often have a bondable coating film, and any composite materials which are bondable to the said matrix alloys.