US3901691A

US3901691A - Aluminum-silicon alloy

Info

Publication number: US3901691A
Application number: US375505A
Authority: US
Inventors: Robert N Sanders; Alex R Valdo
Original assignee: Ethyl Corp
Current assignee: Ethyl Corp
Priority date: 1972-01-20
Filing date: 1973-07-02
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26

Abstract

An aluminum-silicon alloy comprising aluminum as the principal metal, with silicon, magnesium and copper in substantial amounts and iron, titanium, magnesium and zinc in lesser amounts.

Description

United States Patent [191 Sanders et a].

[ 51 Aug. 26, 1975 ALUMINUM-SILICON ALLOY Inventors: Robert N. Sanders, Baton Rouge,

La; Alex R. Valdo, Elgin, 111.

Assignee: Ethyl Corporation, Richmond, Va,

Filed: July 2, 1973 Appl. No; 375,505

Related US. Application Data Division of Ser. Nov 219,523. Jan. 20, 1972.

US. Cl 75/142; 75/141 Int. Cl. C221: 21/02 Field of Search 75/142, 141, 143; 148/32,

[56] References Cited UNITED STATES PATENTS 2,155,651 4/1939 Goetzel n 75/142 Primary Examiner-R. Dean Attorney, Agenl, 0r Firm-Donald L. Johnson; John F. Sieberth; Paul H. Leonard [57] ABSTRACT 2 Claims, No Drawings ALL'NHNUM-SILICON ALLOY This is a division of application Ser. No. 219.523. filed Jan. 20. 1972. now pending BACKGROUND OF THl; INVENTION The present invention is in the general field of matallurgy and relates particularly to non-ferrous metallurgy. The invention is especially related to aluminum' silicon alloys.

It has been previously discovered. US. Pat. No. 2.793.949. that inorganic substances may be incorporated in metals to produce a composite material prod uct. It is taught therein that mixtures of molten metals. including aluminum. and a large variety of inert fillers. including alumina. may be smelted together if the nonmetallic material to be incorporated into the tnetal is wetted by the molten metal used. The wetting agents chosen are those among substances which are capable of lowering the surface tension between the metals and the materials to be incorporated therein. Such prior art also teaches that to modify the structural properties of a metal only slight amounts. less than 1 percent, say ().l percent. of powders or crystal materials should be added to the metal. On the other hand. when the object is to obtain. for example. abrasive compositions. the ratio of hard materials to be mixed with the molten metal should preferably exceed 50 percent by volume ofthe composite product and maybe as high as 95 percent. Although a wide variety of metals and fillers are disclosed. no commercial success has apparently been achieved with the use of any compositions prepared by such process. Also. a number of the compositions disclosed in the reference are highly dangerous. being in fact explosive compositions.

More recently. it has been discovered that a superior aluminum composite can be prepared from aluminum. an alkaline earth metal reducing agent. such as magnesium. calcium. beryllium. sodium. potassium, rubidium or cesium. and a nonmetal filler such as zircon. alumina. Zirconia and aluminum silicates. Sec U.S. application Ser. No. 2l().l27 filed Dec. 20. I971. having a common assignee with the instant invention.

lt is therefore a primary object of the present invention to provide a new and improved aluminum-silicon alloy and composite which has sufficient strength to perform the required or desired use thereof and which is considerably less expensive than presently available aluminum-silicon alloys. especially aluminum-silicon casting alloys.

The instant invention is particularly adapted for use in the manufacture of articles wherein hardness is a principal requirement. An example of such articles are automobile engines or other engines and certain small engine parts.

It is also a primary object of the present invention to provide an aluminum-silicon alloy and contposite thereof which exhibits improved properties such as tensile strength. hardness and toughness.

An important object of the present invention is to provide an aluminum-silicon composite which may be remelted and cast without any significant loss of its physical or structural properties.

Another object of the present invention is to provide a method for manufacturing an aluntinunrsilicon composite of material in which the physical properties may be varied over a wide range as desired. by appropriate changes in the composition.

LII

2 Still another object of the present invention is to provide a new and useful aluminum-silicon composite which is substantially uniform in construction.

Other objects and advantages of the invention will become more readily apparent front a reading of the specification hereinafter.

SUMMARY OF THE INVENTION The invention relates to a new aluminunrsilicon alloy and a new article of manufacture. consisting essentially of an aluminum-silicon composite containing aluminum as its principal element. an alkaline earth metal or an alkali metal. especially magnesium. in sufficient quantity to be an effective reducing agent. and a substantial amount of an inert non-metallic filler such as zircon. alumina. zirconia and aluminum silicates. and a method of preparing said article wherein the alloying elements are heated to sufficient temperature to achieve good fluidity and the filler material is stirred therewith with sufficient stirring to distribute the filler throughout the molten metal. Other elements of the alloy and composite are copper. iron. titanium. magne sium and zinc.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred aluminum-silicon alloy of this invention comprises in percent by weight elements as follows:

Silicon lJ-Zl Magnesium 4&4 Copper 2-4 lron l Maximum Titanium 0.} Maximum Manganese (1.5 Mavimum Zinc 5 Ma timum Aluminum Balance The composite article of the invention comprises three principal ingredients. aluminum-silicon alloy. a metal reducing agent for reducing the surfaces of a non-metallic filler to a metal-like coating. and a non metallic filler which is not subject to being reduced by aluminum metal and which can be effectively reduced by the metal reducing agent. Aluminum-silicon alloys or aluminum and silicon are the preferred principal metals or elements of the alloy composition. Magnesium is the preferred metal reducing agent with other alkaline earth or alkali metals. such as calcium. beryllium. sodium. potassium. rubidium and cesium. being suitable. The alkali metals have a relatively low solubility in aluminum. e.g.. sodium is soluble only to about 0.25 weight percent at 775C. These alkali metals therefore. although being suitable. have somewhat limited use. Preferred non-metallic fillers are zircon and alumina. Zirconia and aluminum silicates are also suitable.

When the composite material or article of this invention comprises magnesium and zircon. the magnesium is preferably in an amount by weight ofabout 2-H) per cent of the liquid phase. with about 4.5 weight percent magnesium producing optimum results. When zircon is used as the non-metallic filler. the zircon may comprise from about 5-30 percent by weight of components. with about lO-4U percent being more preferred and about 30-35 percent most preferred. The amount of magnesium or metal reducing agent required will vary somewhat with the amount of zircon or non-metallic 3 filler in the composite article.

The particle size ofthe filler may vary from about (ill mesh to about 4()() mesh. L'S. Sicvcr Series. with a particle size of lliU/l4tl mesh producing an excellent product. A filler or filler material of a distribution of particle sizes is preferable.

In the most preferred way of preparing or making the composite article of the present invention. aluminum and all metallic and silicon alloying elements except magnesium and zinc are heated to a temperature sufl'i cient to achieve good fluidity. usually about 850C in a suitable furnace or crucible. The temperature necessary will vary with the particular alloying elements selected and the amount of inert filler to be added. The temperature will range between the melting point and the boiling point of the alloying elements. ln general. it is desirable to use as low a temperature as will provide the desired degree of fluidity of the metallic phase.

After the desired temperature has been reached. the magnesium reducing metal and zinc. it zinc is included. are added to the molten metal or alloy. Stirring is commenced and the zircon filler is added. Although the filler may be added cold. it is preferably preheated to a temperature of about that of the melt. Stirring is continued until the filler is dispersed throughout the molten metal. usually about 5 minutes. The time of stirring will vary somewhat with the amount of filler added. and in general as short a stirring time as necessary to achieve adequate particle distribution is preferred. Optimally. the mixture is stirred until the filler is substantially equally distributed throughout the melt.

After mixing or stirring the molten mixture is cast in the form of ingots or other desired shapes.

When using a pro-prepared or standard aluminumsilicon-magnesium alloy as the metallic phase. the alloy is heated to temperature and the non-metallic filler is added thereafter. The molten mixture is stirred sufficiently to draw the filler into the molten phase.

In another way of carrying out the present invention. all of the ingredients of the composite article. except the metal reducing agent. preferably magnesium. are mixed together and heated to temperature. Magnesium is then added and the mixture stirred. Dross is skimmed from the molten mixture and the melt is then cast. This procedure reduces dross.

The aluminum composite or article of the instant invention may also be prepared by mixing all of the components of the article. namely aluminum. silicon and other elements, metal reducing agent. and non metallie filler. together. then heating to desired temperature and stirring. The dross is skimmed from the melt and the molten mixture is poured into a mold and cast into a suitable shape. This procedure is preferably followed under an argon purge. Such a purge eliminates some dross from forming.

Hardness of the aluminum-silicon composite is increased by subjecting the composite to a three-stage heat treatment as follows:

a. conducting a solution heat treatment at 80()l 0UtlF for about 4 to 24 hours followed by a quench; b. conducting a precipitation heat treatment 2()()-3(llll-' for about l2 to 36 hours; and c. conducting a second precipitation heat treatment at ln order to facilitate understanding olthe invention. the following examples are illustrative thereof; how ever. it is understood that these examples do not limit the scope of the invention in any fashion.

(mil

(iENfRAl. PROCEDl'RlZ The apparatus consisted of an electric heating element inside a l'irebrick housing. a foundry crucible. a motor-driieu stirrer and a carbon rod bal'lle. Alumi hum-silicon alloy and non-metallic filler. such as zircon or alumina were mixed in the crucible. heated to tem perature and stirred. The charge was then poured into a crucible. After cooling. the casting was measured for hardness on a Rockwell tester Using the l: or B scale as appropriate. Hardness reading were recorded with standard deviation. The casting was then given a precipitation heat treatment at 250F for 24 hours with an air quench. On some castings. a second precipitation heat treatment was conducted at 350% for 8 hours. Hardness was measured on the Rockwell l'ester after each heat treatment. Solution heat treatments were also conducted on some samples at l()(l()F for 16 hours. Hardness was also measured after these treatments.

Particle size distribution of the alumina and zircon fillers were as follows. unless otherwise specified:

Welghl Percent A sample of a commercially available alloy suitable for use in automobile engines hereinafter referred to as Alloy A was prepared by mixing 766 parts of Al. l7O parts of Si. 45 parts ofCu. lU parts of Fe. 5 parts of Mg. 2 parts of Ti. 1 part of Mn. and l part of Zn. This mixture was heated under argon at 850C and cast. The cast plug was placed in a 600C oven for 8 hours and completely melted. It was cooled. sawed into pieces. remeltcd at 550C and cast. The alloy had a Rockwell E hardness of 87.8 i 3.0 (standard deviation). The specimen was given a precipitation heat treatment at 250F for 24 hours with an air quench. after which it had a Rockwell B hardness of 76.6 t 4.8 (standard deviation).

EXAMPLE 2 The following were mixed. heated to 850C for l hour and stirred for a brief period: 695 parts of Al. I parts of Si. 40 parts ofCu. 9 parts of Fe. 62 parts of Mg. 2 parts ofTi. l part of Mn. and 1 part of Zn. The alloy (Alloy l was cast and cooled. The rockwell E hardness on the resulting casting was 78.5 i 1.4 (standard deviation). The specimen was precipitation heat treated at 250F for 24 hours with an air quench. The Rockwell B hardness on the specimen was then 59.3 i 3.3 (standard deviation). The specimen was then given another precipitation heat treatment at 350F for 8 hours. This resulted in a Rockwell B hardness of 68.3 i 2.0 (stan dard deviation).

EXAMPLE 3 720 parts of Alloy l were recovered from Example 2. To this alloy was added 388 parts of ground zircon and the mixture was heated to 850C under an argon purge. then stirred for 5 minutes. The Rockwell R value was 46.5 9.3 (standard deviation) on the resulting specimen. After 24 hours at 250F. the hardness increased EXAMPLE-i 5 A specimen front Example 3 was given the same solu tion heat treatment and quench as in Example 4. The

to 61.2 i 8.3 (standard deviation). and an additional 8 5 resulting Rockwell E hardness was 80.0 i 3.1 (standard hours at 350F resulted in a value of 64.7 i 9.7 [standeviation). and the usual two-step precipitation heat dard deviation). treatment resulted in Rockwell B values of 66.2 i 1.2

(standard deviation). and 72.5 t 9.9 (standard devia- EXAMPLE 4 1 tion).

Beginning with this example. the ceramic crucibles The results obtained in Examples 2. 3. 4 and 5 are were replaced with 4 inch steel pipes which were sealed summarized in Table l. hereinafter. This Alloy 1. conat one end and giv'enfour coatsofCarborundum Fibersisted of. by weight. 695% Al. 190% Si. 4.09% Cu. frax Coating Cement. Type QF-l80. The stirrer was 0.9% Fe. 6.2% Mg. 0.2? Ti. 0.1% Mn and 0.17: Zn. similarly coated. The charge consisted of 464 parts of The alloy incorporated 3571 zircon filler with no appar- Al. 127 parts of Si. 27 parts of Cu. 6 parts of Fe. 4] ent difficulty. Significant improvement of alloy is obparts of Mg. 1.3 parts of Ti. 0.6 parts of Mn and 0.6 tained with a two-step precipitation heat treatment. A parts of Zn. This Alloy 1 mixture was heated to 850C solution heat treatment at 925F for one hour followed as usual. 233 parts of ground zircon were stirred in the by a simple precipitation heat treatment was less effecalloy mixture over a 2-minute period. then the stirrer tive in hardening the alloy samples. The addition of the speed was increased and stirring continued for an addi filler did not significantly decrease the effectiveness of tional 2 minutes. Large pieces of undissolved silicon the two-step precipitation heat treatment. A solution were clearly visible in the casting; therefore. it was disheat treatment at 1000F for 16 hours followed by a carded. two-step precipitation heat treatment showed promise Thirty parts of Cu. 521 parts of A1. 143 parts of Si. of significant improvement. Some high temperature ox- 6.8 parts of Fe. 1.5 parts of Ti. 075 parts of Mn. and 35 idation damage was indicated. but this can be easily 0.75 parts of Zn were mixed together and heated to prevented by the use of an inert atmosphere during the 850C in the usual way. After minutes. the stirrer solution heat treatment. The protected side hardness was submerged and 46.5 parts of Mg were added. After value of 81.4 t 5.2 compares very favorably with the 5 minutes of stirring. the stirrer was removed. and then hardness of 76.6 t 4.8 obtained for Alloy A.

TABLE I Rockwell 1n Precipitation Heat Treatment Solution Heat Treatment Hardness Temp Time. Rockwell B Temp. Time. Rockwell lzl Temp. Time. Rockwell E S)stcm As L'a\e" hr. Hardness "F hr. Hardness F hr. Hardness Alloy A 87.8 t .1 u 250 24 76.6 14.x

Allo) 1 7x5 |.4 25a 24 59.3 i 3.3 351) s 0&3 2.0

'; lircon 46.5 93 250 24 61.2 s3 35!) s 64.7 :9 7

W 25a 24 61.2 i 1.2 3511 s 72.5 t 9.9"" lnou l6 sun 1* 1.1

Alloy 35'; Zircon 761 1 l 250 24 ms :01) 3511 x 67.5 |.7

"" 250 72 63.2 |:.1 35H 8 64.2 i 16.9" man 16 s4 2 7.4

""Rocknell H Hardness "lop side \.ilne

EXAMPLE 6 resubmerged after 10 minutes. After 5 minutes had passed. 350 parts of ground zircon were stirred in the mixture. This took about 2 minutes; then the stirrer speed increased and stirring continued until a total of 5 minutes had elapsed. The Rockwell E hardness value was 76.1 i 1.1 (standard deviation). After 24 hours at 250F the hardness value had increased to 90.8 i 0.9 (standard deviation). The specimen was then heated to 350F for 8 hours with the result that the hardness increased to 67.5 i 1.7 (standard deviation) on the Rockwell B scale.

A solution heat treatment at 1000F for 16 hours was then given and the specimen water quenched. The Rockwell E value was 84.9 i 7.4 (standard deviation). Repeating the two-step precipitation heat treatment from above resulted in a Rockwell B value of 63.2 I 12.] (standard deviation) after the first step and after the second step. atop side value of 64.2 i 16.9. and a bottom (protected) side value of 81.4 i 5.2 were ob tained.

An alloy was prepared to simulate one which would be obtained by using primary reduction alloy as the silicon source. 353 parts ofa 60% Al. 3571 Si. 3 /1 Fe. 271 Ti alloy were mixed with 231 parts of Al. 26 parts of Cu. 0.5 part of Zn. and 0.5 part of Mn and heated to 850C as usual. After'l hour at temperature. 39 parts of Mg were added and after 5 minutes stirred for 2 minutes. After an additional 18 minutes. 350 parts of ground zircon were stirred in the alloy with a gradual increase in stirring speed until a total of 5 minutes has elapsed. The product was much too viscous to pour.

EXAMPLE 7 One-hundred thirty parts of powdered silicon. 39 parts of Mg. 26 parts of Cu. 65 parts of Zn and 390 parts of Al were mixed and heated to 850C as usual. and following the same procedure as in Example 6. 350 parts of ground zircon were stirred in with the same resalts as in Example 6. Repeating this example using a different crucible and a thermocouple check gave the same results.

EXAMPLE 8 Example 7 repeated using lump Si in place ot powdered Si. After successful casting and the above series 8 under an argon purge. the stirrer was submerged and 70 parts ol'Zn and 42 parts of Mg were added. The ten sile specimen mold was heated to 850C and the other two molds to 670C. Using usual stirring procedure.

of heat treatments. The Rockwell B values. with stan- 300 parts of zircon were stirred in. then a C1 purge dard deviation were in order: 963 i 4.4; 94.0 i 8.0; given and the ladle used to till the molds. The molds did 94.0 i 6.0; 99.6 i 4.0; and finally 100.4 3.9. not fill well and there were large quantities oi unincw porated powder. excessive deterioration of the stirrer IZXAMPLE 9 was also noted.

Exactly the same procedure as in Example 8 was lol- 11) The above example was repeated using a new stirre. lowed except that alumina was used in place of zircon. and a new steel tensile specimen mold. Flame was The material could be poured but was too viscous to fill noted during the addition of the zircon (a newly comthe mold well. As cast. it had a Rockwell B value with posited and ground sample was being used). The tensile standard deviation of 703 1.9. and after 5 days of specimen was broken in the constricted rc' m The natural aging it increased to 81.6 i 5.8. Rockwell B hardness value was 92.5 i 4.! \tter 16 hours at 1000F under purge followed by a water EXAMPLE quench. the Rockwell B hardness value was 84.0 i 4.0.

The procedures of Example 9 were repeated except The usual two-stage precipitation heat treatments gave 3071 A1 0, was used in place of 35 /1. An excellent east- 85.7 :t 4.8. and 87.0 :t 3.2. respectively. The above ex ing was obtained. 20 ample was again repeated except that no tensile specimen was poured. the liquid was poured rather than la EXAMPLE I l dled. and the hardness mold was coated with one coat The following were mixed and heated to 850C in the of Fiberfrax cement and maintained at 500C. Flaming usual way: 465 parts ofAl, 124 parts of Si (powdered). was again noted. After casting and cooling. the Rock- 13 parts ofCu. 5.6 parts of Fe. 40 parts of Mg. 1.0 part well E value was 89.0 i 2.2. Repeating the above exof Ti. 0.7 part of Mn. 0.7 part of Zn. After 1 hour at cept a l-hour soak at temperature before the stirrer temperature. 350 parts of ground zircon were stirred in was submerged. again resulted in flaming. As cast. soluas above with the same results as in Example 7. The extion heat treated. and two step precipitation treatments ample was repeated except that lump Si was used in gave. in order. Rockwell B values of 60.8 i 11.3; 55.9 place of powdered Si and the Mg was not added until 39 t 9.9; 63.9 i 8.9; and 78.6 i 2.4. just before the ground zircon. In this case. a fluid sys- Changing procedure. 420 parts of Al. 140 parts of Si. tem resulted. A specimen was cast and cooled. The and 28 parts ofCu were mixed and heated to temperaspecimen had a Rockwell B hardness of 82.8 t 12.2 ture and maintained for 1 hour with normal stirring (standard deviation). Regular solution and two-stage every 10 minutes. The stirrer was submerged. the temprecipitation heat treatment were given except a nitroperature allowed to recover. and 42 parts of Mg and 70 gen purge was used during the solution treatment and parts of Zn were added. In this case. 300 parts of 72 hours elapsed between solution and precipitation ground zircon were added and the above procedure folheat treatments. The resulting Rockwell B values with lowed from this point. There was no indication of any standard deviation were 84.0 i 8.8; 91.0 i 12.6; 85.0 flame. The same series of treatments as above were i 11.3; and 90.4 i 5.2. respectively. given with these respective Rockwell B hardness val- 'J 1 EXAMPLE l2 ues. 47.3 12.8. 69.6 7.0. 69.9 9.8 and 71.3 7.8.

Normal heating and mixing procedures were used hXAMPLE with 330 parts of A1. 110 parts of Si. 22 parts of Cu. A new alloy system was prepared by mixing 518 parts parts of Zn. 33 parts of Mg and 450 parts of ground zir- 45 ofAl and parts ofSi and heating to 850C and maincon. The mixture was too viscous to pour. Repeating taining for 1 hour. Then 42 parts of Mg were added the example with 360 parts of A1, parts of Si. 24 along with 70 parts of Zn. The usual procedure was folparts of Cu. 36 parts of Mg. 60 parts of Zn. and 400 lowed from that point including a Cl purge. Neither parts of ground zircon gave results similar to those obtest specimen was of any use. tained in Example 9 on castability. As cast. the Rock 51) The above was again repeated except all metallic inwell B value was 89.4 i- 4.1. after solution treating 88.9 gredients were mixed at the beginning and no C1 purge i 6.7. and precipitation heat treatments gave Rockwell was given. The as cast solution and two-stage precipita- E values of 95.3 i 3.2. 212 and 98.3 t 2.1. tion (Rockwell E hardness) values were. in order: 63.4

i 2.8. 77.6 i 6.4; 79.8 i 3.7; and 84.7 14.7. EXAMPLE 55 The alloy compositions of Examples 7-l4 are sum- Four-hundred twenty parts of aluminum. parts o1 marized in Table I1 hereinafter. Si and 28 parts of Cu were mixed and heated to 850C TABLE 11 Elements and Filler 111 Percent by Weight A1 Mg Si Cu Fe 11 Mn 7n [.ircon Alumina and 8 390 3 9 13.1) 2.0 65 35.0 I'.\. .w 11 3 9 13 0 :1 n 5 35.11

Ins 111 4: u 4 3 14.11 1 s .0 311.11 l.x 1| 4115 4.11 124 1.1 (I5 (it til n1 35.0 l 12 3.1!! 3.3 1111 22 s 5 l.\. 13 4:11 4 2 1411 3 s 7 a tuna TABLE ll-continued lzlemcnts and llllt.l' iii Percent by Weight .-\I Mg Si (ti l-e li Mn Zn [.ireoii Alumina i-\ 14 Ms 4.: 7.11 7.0 1000 When the same ratio of components. with the exception of the magnesium content. as was the case with Alloy A. was used as a basic alloy for a filler experil lABLE llLCOmmucd nient. considerable experimental difficultics were en Brim." Hmdm.s countered and a very poor product was obtained. PHLiPiRIIiWI lhc basic reason for the significantly harder than M Hum Fm Sccmd usual nature ot Alloy A is the presence of crystalline Alloy 2 Case Treatment Stage Stage i V s I silicon in a metal matrix. lhat alloy contains l7((-Slll t5 oupum Zirclm 8] I25 25 H] con and the eutectic mixture for aluminum and silicon is l l.7. Therefore. about onc-third of the total silicon would crystallize out on cooling and be dispersed in the metal matrix. In the case of Alloy A there is no other EXAMPLE l6 component that would use up any significant amount of the excess silicon. When one adds sufficient amounts of magnesium to allow incorporation of the filler one has a different situation. Magnesium reacts with silicon to form the intermetallic Mg Si and thus significantly reduces the amount of Si which is free to crystallize out. Thus. one significantly reduces the hardness of the alloy. A new alloy was prepared that was designed to have the same amount of silicon free to crystallize out after allowance was made for the silicon removed as the magnesium silicon intermetallic. This new alloy as cast was 8571 as hard as Alloy A which may be due to the presence of the intermetallic. After the 250F precipitation heat treatment to obtain the beneficial effects of the copper content. the hardness increased by 5l'/i to l07 Brinell number which was 75% of Alloy A value at that point. After the 350F precipitation heat treatment which was beneficial the Brinell number was 121. which was an increase of 12% over the previous value and 86)? of the final Alloy A value.

Such an alloy produces an excellent metallic phase for a filled aluminum product.

There are very significant results contained in the foregoing examples. The Rockwell B hardness of l00.4 t 3.) obtained in Example 8 is unique amont casting alloys whose value is considerably less in the majority ofcases and reaching higher values only in such special cases as the Alloy A engine alloy. Even wrought alluminum alloys do not generally reach this value. Such a product is comparable with brass in hardness.

EXAMPLE 15 Brlnell Hardness Precipitation Solution Heat 1 reatment As Hciit First Second Alloy 2 (use l'reiitment Stage Stage Zircon Wit lb] I69 I73 iron tFlami. during addition t I08 I01 H4 I46 LII Tensile strengths of Alloy 2 with 35% zircon were determined and the results are illustrated in Table IV as follows:

TABLE IV Yield Ultimate Strength Strength Percent Composite kpsl kpsi Elongation Alloy Z 357/ Zircon 3.6 13.5 5.3

EXAMPLE [7 Hardness and tensile strength of various alloys were compared as a function ofthe level of zircon loading at various percentages from 0 to 30 for alloys as follows:

Percent by Weight of Elements in Metallic Phase Similar tests using bismuth, a more effective metal at lowering surface tension. showed that bismuth was not capable of reducing the filler surface and was completely ineffective in producing a satisfactory composite article. Other tests using quartz as a filler indicated that the filler must be sufficiently stable so that it will 1 1 not be reduced by the aluminum. but must be reduced by the metal reducing agent. namely magnesium.

The foregoing tests and other tests. showed that to obtain successful results a 25609? by weight tiller level. there must be effective stirring. The stirrer must also be in good condition and run at effective speeds. When contact times are on the order of 5 minutes. a minimum of about 471 by weight of magnesium is required to produce a satisfactory product. At a higher percentage of magnesium loadings, the contact time may be shorter. Stirring or contact time and amount of filler go together. The degree of reduction of the filler is determined by the kinetics of the reduction which in turn is dependent on the concentration-time ratio.

Once the powdered filler was incorporated it showed little tendency to separate by any mechanism other than Stokes law settling of the particles. Settling is quite slow because of the smallness of the grains. the high vis cosity of the metallic phase and the extreme similarity of the particle and melt density. especially with alumina as the filler. Uniquely. no separation of particles was observed when the filled products were remelted and recast.

An increase in temperature of the mixture of about C was observed when the filler was added. This in crease is due in part to stirring and chemical reaction.

Tin. which is an effective metal for reducing surface tension of aluminum. would not provide the reducing action necessary for a successful productv Hardness is a physical property that will have an effect on the useability of the filled product as a replacement for other aluminum-silicon casting alloys. The normal hardness range for such casting alloys is from a Brinell number of about 50 to a Brinell number of about I20.

It may be seen that while there is a significant increase in hardness between the basic aluminum-siliconmagnesium alloy and the same alloy with filler. i.e., a factor of about 2 with alumina and about 3 with 25% zircon, the best values obtained are still in the lower portion of the desired range.

Some control of the physical properties of the aluminum-silicon composite of this invention may be obtained by selection of an appropriate filler material. lfa

I 2 tough cut or drill resistant composite at some sacrifice of density is desired. Iircon may be selected as a filler. If such properties are of less importance and low den sity is desired. alumina would probably be selected as the filler.

The volume of the tiller in the metallic phase is the crucial factor in determining the amount of filler that can be accepted by the metallic phase and still retain metallic like properties. The weight percent of tiller that may be used is different for each filler and is de pendent upon the filler density.

Intricate castins can be satisfactorily produced using the molten filled aluminum-silicon composite of this invention with little or no loss of desired physical properties as compared with a comparable unfilled aluminum-silicon alloy casting.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes may be made within the scope of the ap pended claims without departing from the spirit of the invention.

What is claimed is:

1. An aluminum-silicon alloy consisting of elements in percent by weight of about as follows:

Silicon l9-2l Magnesium 4-8 Copper 2-4 Iron l Maximum Titanium (L3 Maximum Manganese 05 Maximum Zinc 0.5 Maximum Aluminum Balance.

2. The alloy of claim 1, wherein the elements are present in percent by weight about as follows:

Silicon i9 Magnesium 6 Copper 4 iron I Maximum Titanium 0.3 Maximum Manganese 0.5 Maximum Aluminum Balance.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 91

DATED August 26 1 1975 |NVENTOR(S) l Robert N. Sanders and Alex R. Valdo it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 44, "amont" should read among Column 10, line 44, "Table B" should read Table V Column 10, line 48, under Column 15, "96.2" should read 86.2 Column 12, line 12, "castins" should read castings Eignccl and Scalcd this [SEAL] twenty'mi'd D y 0f December 1975 A ttesr:

RUTH C. MASON (nmmissiuner nfParenrs and Trademarks