US1508556A

US1508556A - Making castings of aluminum alloys

Info

Publication number: US1508556A
Application number: US435024A
Authority: US
Inventors: Jeffries Zay; Robert S Archer
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1921-01-04
Filing date: 1921-01-04
Publication date: 1924-09-16
Anticipated expiration: 1941-09-16

Description

Patented Sept. 16, 1924.

UNITED s'rATEs 1,508,555 PATENT OFFICE.

ZAY JEFFRIB, OF CLEVELAND HEIGHTS, AND ROBERT E. ARCHER, 0]! EAST CLEVE- LAND, OHIO, ASSIGNORS TO ALUMINUM COMPANY OF AMERICA, 01' PITTSBURGH, PENNSYLVANIA, A. CORPORATION OF PENNSYLVANIA.

MAKING OASTINGS OF ALUMINUM ALLOYS.

Jo Drawing.

To all whom it may cmwem:

Be it known that we, ZAY Jnrrams and Roman S. ARCHER, both citizens of the United States of America, residing at Cleveland Heights and East Cleveland, respectively, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in Making Castings of Aluminum Alloys, of which the following is a full, clear, and exact description.

This invention relates to the production of aluminum alloy castings particularly castings made of alloys containing silicon or copper or both, with or without other metals, and its chief object is to provide a simple and effective method which will produce light-weight castings with a hitherto unobtainable combination of physical properties, especially as regards elastic limit, tensile strength and ductility. To this and other ends the invention consists in the novel method hereinafter described.

As will be seen from the subj oined description, the invention is based upon the combination of certain steps, some of them novel with us, and in art the invention resides in the discovery t at certain alloys are especially susceptible to improvement by heat treatment after casting, and that certain methods of casting such alloys further and peculiarly adapt them to such treatment; and in the additional discovery of temperature and duration of heat treatment in combinations appropriate to the particular alloys and methods of casting involved. With the aid of these discoveries we have been able to produce castings having improved hysical properties with respect to elastic imit,

tensile strength and ductility to an extent hitherto unattainable, with the result that it is now possible to use aluminum alloy castings for purposes for which their use has previously been impracticable.

It has been found that the addition of a substantial amount of silicon to aluminum alloys very materially improves their casting qualities, thus rendering it possible to successfully and easily make castings which would otherwise be very difiic-ult to roduce. In particular, the presence of a su stantial amount of silicon enables us to produce alloys having excellent casting qualities, even better than those of the well known alloy containing 8 per cent copper, with the Serial No. 435,014.

use of only relatively small amounts of copper or zinc or both. The possibility of limiting these heavy metals to amounts of say 5 per cent or less in the case of copper, and 10 per cent or less in the case of zinc, is very advantageous both' as respects the strength of the resulting alloy and as respects its specific gravity. The silicon, by virtue of its lightness, offsets, in a measure the effect of the heavy metals, copper and zinc, as well as permitting the use of the heavier metals in smaller quantities. We have discovered that these silicon alloys can be materially improved by an appro riate heat treatment, which may affect hot the silicon and the heavy-metal constituents.

The tensile strength of commercially pure cast aluminum is about 12,000 pounds per square inch and its elongation about 25 per cent. By adding varying proportions of hardening metals, particularly copper and zinc, it is possible to increase the tensile strength so that the sand cast alloy will have an ultimate strength of nearly 30,000 pounds per uare inch, but the elongation is there by re need to less than 5 per cent. By adding a very large amount of zinc the tensile strength may be raised to a proximately 40,000 ounds per square inch, but the elongation is reduced to almost nothing, and the alloy is very brittle. By casting any of these alloys in a chill mold the tensile strength may be increased in general by approximately 5,000 pounds per square 1nch and the elongation may also be increased. But it has heretofore been impossible to simultaneously produce tensile strengths of over 30,000 pounds per square inch and an elongation of 8 per cent or over.

By our method, however, we have been able to extend very greatly the range of the tensile strength and elongation, and of the combination of the two, so that we have obtained castings having very much higher tensile strengths than those hitherto known in the art, and yet elongations better than those at present obtained with casting alloys having only moderate tensile strengths.

In general, elongation decreases as tensile strength increases, but our new method enables us to produce very much better simultaneous results in both of these respects than have hitherto been possible.

It is also to be noted that the high tensile strength alloys previously known have require the presence of substantial amounts of zinc, even 1n many cases up to 33 per cent,

and have therefore been considerably heavier than pure aluminum, while we obtain our rsults with an addition, in general, of not more than 5 to 10 per cent of total heavier alloying metal or metals and yet produce a casting which is notonly stronger and more ductile but likewise lighter than would otherwise be obtained.

Various prior investigators have proposed to obtain castings possessing the desirable combination of high tensile strength and ductility by heat treatment of a properly made castin but their contributions to the art have so ar not led to commercially useful results. For example, the best results ublished prior to our work are those of ilm, who reports having obtained castings with a tensile sterngth of about 32,000 pounds per square inch and an elongation of 5 to 7 per cent. More recently Menca and Karrhave by heat treatment of an alloy containing copper and a large amount of zinc, obtained. a tensil strength of 41,200 pounds per square inch but with an elongation of only 4 per cent. This alloy contained about 19 per cent ofheavy alloying metals and hence had a specific gravity greater than 3. With lighter alloys, for example one containing small amounts of copper, magnesium and manganese, they obtamed a tensile strength of 35,500 pounds per square inch and an elongation of 2.3 per cent. In none of the three cases mentioned above were the properties enough better. than those possessed by untreated castings to justify the cost of the treatment.

Our invention involves the discovery of important reasons for previous lack of practical success along this line. and embraces a combination of old and new steps so that we are now able by means of our improved method to produce articles. cast in either sand or chill molds, having physical properties far superior to those of any such castings hitherto produced. By means of our novel method we have produced sand castings of an aluminum alloy containing 4 per cent copper and 0.2 per cent m esium. having a tensile strength of about 50,000 pounds per square inch and an elongation of 8.5 per cent, with relatively high elastic limit; also chilled castings having a tensile strength of 54,000 pounds per square inch and an elongation of 18 per cent, with relatively high elastic limit.

This combination of high tensile strength and elongation enables these castings to be used for purposes for which aluminum castmgs have not hitherto been suitable and for which it has been necessary to use the much heavier ferrous materials such as steel or malleable iron.

neoaue One example of our process comprises as its first step the preparation of an aluminum alloy containing about 3 to 5.5 er cent copper, preferably 4 per cent, witli no magnesium or with magnesium up to about 0.3 per cent, the iron content in particular being as low as possible, preferably not to exceed 0.25 per cent. Iron and silicon are always present as impurities in aluminum as now obtainable, and a art of our invention consists in so choosing the raw'materials as to limit the iron content of the finished alloy to an amount as low as possible, referably not over 0.25 per cent. The use 0 silicon in substantial amounts will be considered hereinafter.

The ingredients are mixed in the molten state, care being taken to avoid excessive tem eratures at all stages of the melting operation, and the mixture is poured into either a sand mold or a chill mold, and caused to solidify. After solidification a IIllCI'OSCOPlG examination reveals masses of an aluminum-rich constituent surrounded by a network of a hard, brittle constituent, which has been reported to be chiefly CuAl In the form of a sand-cast test bar about one half inch in diameter the alloy has a tensile strength of 18,000 to 25,000 pounds per square inch with an elongation of 2.5 to 4: per cent in two inches. A chill cast test bar of the same size has a tensile strength of about 24,000 to 28,000 pounds per square inch and an elongation up to 6 per cent in two inches. The iron in the alloy is found both in the form of needles, reported to be FeAl,, and in a different form, apparently as a silicide of iron. The presence of the iron (FeAl,,) needles up to a certain amount is beneficial to the strength and ductility of the alloy in the cast condition, probably due to the fact that the ordinary path of fracture in the cast alloys is through the brittle network of CuAl, which is strengthened by the iron needles. It is found that these iron needles are very detrimental to the physical properties of the casting after the heat treatment discussed below.

The next step in the example of our processnow being described consists in heating the castings to, and maintaining them at, a temperature of 500 to 540 C. for a riod of time depending upon the results 5 sired and the manner in which .the casting was made. The principal object of heating the castings at the temperature mentioned is to cause the CuAl in the network to go into solution in the solid aluminum-rich constituent. It is found that at the tem ratures referred to, this CuAl dissolves s owly, in fact surprisingly slowly. In sand castings the time necessary for maximum solution of this (LuAl may be as much as 48 hours, at the temperatures mentioned; while in chill castings, because of the finer network structure, the time for maximum solution is less,-

for example, 7 hours has been found to be sufiicient in some cases.

If the copper content exceeds the amount which is soluble in the solid state just below the freezing oint of the eutectic, some of, the CuAl will remain in the network after heat treatment, and the physical properties of the castin will not be as good as can be obtained wit a lower copper content. In most if not all cases the best combination of physical properties results only when sub stantially all of the CuAl in the network has been dissolved in the aluminum-richconstituent.

A temperature of heat-treatment high enough to fuse the eutectic is in most cases unfavorable to the best ultimate results, and it has been found that in some instances 540 (J. is too high unless the rate of heating up to that point is very slow or the time of heating below that point is comparatively ong.

A further result of heating the castings at the temperature mentioned is to re-dissolve any CuAl which may have precipitated in small particles within the aluminum-rich constituent rather than in the net- Work during the previous cooling of the castings.

After the heating period the castings are preferably cooled rapidly, as by quenching in water. By the above described procedure, sand castings of an alloy containing 4 er cent copper, 0.2 per cent magnesium and ess than .25 per cent iron have been produced with a. tensile strength, after aging, of about 50,000 Pounds per square inch and an elongation o 8.5 per cent. Chill castings have been made by the same process, of the same alloy, having a tensile strength of 54,000 pounds per square inch after aging and an elongation of 18 er cent.

As stated above, quenchmg is preferable to slow cooling, but good results can in some cases be obtained by cooling in a current of air. A marked difi'erencehas been observed between the results obtained by cooling in a. current of air and those obtained by cooling in still air. Even slow cooling, however, produces improvement as compared to the cast condition, not only in the physical propcrties but also in resistance to corrosion.

The physical properties of castings subjected to the treatments above referred to can be further changed by heating, immediately after cooling, to a temperature of 100? to 150 C. for a time, one hour being in many cases sufficient. As a result of this heating the tensile strength is increased and the elongation decreased, and the elastic limit is increased very markedly.

The method of casting is an important factor. Thus a method producing fine grain and improved physical properties,

yields castings which are generally more amenable to the heat-treatment than does a casting method which produces coarse grain. For example a bar having a cylindrical test section two inches long and a half-inch in diameter, composed of alloy containing about 4 per cent copper and cast in a sand mold, has a tensile strength of about 18,000 pounds per square inch and an elongation of about 4 per cent. If the bar is heat-treated by our method. say at a temperature around 520 C. for 24 hours, the tensile strength may be more than doubled (increasing to about 37,000 pounds per square inch) and the elongation is increased to about 12 per cent, or three times its original value. On the other hand, if the bar is cast in such a manner as to cause rapid solidification, say by chill casting in an iron mold, it will have, after heat-treatment by our method, a tensile strength of about 40,000 pounds per square inch, and an elongation of about 20 per cent.

In sand castings of alloys containing substantial amounts of silicon a considerable portion of the latter appears in the form of relatively large plates or needles, and in chill castings the silicon is found generally in smaller particles, some of Which at least are more or less rounded. The heat-treatment changes the shape and sometimes the size of the silicon particles, tending toward a more rounded form, and the improvement in physical properties produced by the heattreatment of such alloys 18 due in part to this change.

The addition, to the aluminum-copper alloys, of a small amount of magnesium, say 0.2 or 0.3 per cent, increases the tensile strength and elastic limit, but is less favorable to ductility or elongation. Magnesium may also be added to the aluminum-silicon alloys, the effect, generally, being to increase the tensile strength and diminish the elongation.

For the best results. our experience indicates that the iron content of the aluminum taken to make the castings by the chill method, a higher percentage of iron can be used, good results being obtained with chill castings containing even more than 0.4 per cent of iron. On the other hand, in the case of heat-treated sand castings. more than that amount of iron gives less advantageous physical properties. The presence of the iron is evidenced by crystalline needles. probably of the composition FeAl which usually form in the network containing CuAL These needles are not soluble to any considerable extent in the solid aluminum alloy, and remain intact and in lace while the CuAl, is absorbed into the body of the solid-solution crystals of aluminum during heat-treatment. The iron needles tend copper alloy should be low, but if care is v to have a beneficial eifect on the physical properties of the alloy as cast, that 15 before heat-treatment, but after the (hull in the network has been dissolved into the aluminum-rich constituent by heat-treating, the iron needles are a source of weakness, diminishing both tensile strength and elongation.

The complete elimination of the iron needles is therefore highly desirable, but the complete avoidance of iron or even its reduction below about 0.25 per cent is not always practicable commercially. -However, when silicon is present in excess of the iron, the quantity of FeAl formed is lessened, and some of the iron combines with the silicon to form what appears to be an iron silicide. We have discovered that the latter compound freezes in a form less harmful than the needles of FeAl,. In the case of chill castings, it is found that the FeAl needles are much smaller than in the sand castings, and hence they are not so objectionable in the heat-treated casting. Since there is considerable difliculty in commercially producing aluminum free from or containing less than 0.25 per cent of iron, the desired silicon-iron relationship is most advantageously obtained by adding silicon when necessary. For example, if the iron content of the aluminum ingot is 0.35 per cent and the silicon 0.3 per cent, we find it advantageous to add about 0.35 per cent silicon. We have also found that the addition of a small quantity of zinc, say 0.25 per cent, improves both the tensile strength and elongation of the heat-treated castings.

Chromium up to 0.5 er cent or a little more increases the tensile strength in the heat-treated casting, but reduces the elongation.

With regard to the limits of copper content, we have observed that up to about 2 per cent copper, nearly all the OuAl re- -mains in solution upon solidification, and

that beyond 5.5 per cent copper some of the (JuAl usually remains out of solution even after heat-treatment. In some cases the metal can be heated above the melting point of the eutectic of CuAl and aluminum without impairing its physical properties provided the metal is cooled to a temperature slightly below that of complete solidification and held there for some time before quenching. When substantial percentages of iron, silicon, magnesium and zinc are present, or any of them, the higher permissible temperature is lowered.

A very important class of alloys embraced by our invention includes the use of silicon in substantial amount, say from 3 to 15 per cent. With the silicon class of alloys the nest results are usually obtained when the castings aremade in a chill mold. For example, a chill cast test bar of. an alloy containing about 10 per cent silicon and no copper showed a tensile strength around 30,000 pounds per square inch and an elongation of about 7.5 per cent in two inches. After heating at 560 C. for 40 hours, followed b quenchin the tensile strength was about ,500 poun s per square inch, but the elongation was found to have been increased to 21 per cent. We are therefore able to pro duce by our method a casting of aluminumsilicon alloy having great ductility and at the same tlme a tensile strength twice or more than twice that of aluminum, with the further advantage of good casting qualities as mentioned above. The addition of copper to this aluminum-silicon alloy increases the tensile strcngth enormously but decreases theelongation. Chill cast bars of an alloy containin 6 per cent silicon and 4 per cent copper, heated 45 hours at 500 to 515 C. followed by quenching, showed a tensile strength as high as 42,000 pounds per square inch and an elongation of 8 per cent. In the high silicon alloys the most advantageous copper content is from 2 to 5 per cent. It should be noted that the eutectic of the aluminum-silicon system melts at 570 to 580 (1, which is higher than the melting point of the aluminum-copper eutectic which is at 540 C. and therefore it is not only permissible but advantageous to heattreat the former alloys at higher temperatures,-say 530 to 570 C. When copper is added to the aluminum-silicon alloys a ternary eutectic may form with a melting point of about 520 C. and consequently the heat-treatment temperature should be lowcred accordingly. Zinc and magnesium also lower the maximum heat-treatin temperature of the aluminum-silicon al oys.

Zinc can also be added to the aluminum alloys containing substantial amounts of silicon and co per or either of them. For example an aliby containing 8 per ccnt.silicon, 10 per cent zinc and 2.5 per cent copper, gave a tensile strength of 32,300 pounds per square inch, and an elongation of 2.5 per cent in 2 inches in a chill cast test bar, and after heat-treatment similar to that mentioned above the tensile strength was increased to over 44,000 pounds per square inch and the elongation .to 7 per cent. In case only silicon and zinc are present, it is found that the heat treatment has a less beneficial effect on the tensile strength, but the elongation is very favorabl afi'ected. For example, in an alloy containing 8 per cent siliion per cent. It is also found that the heattreatment can be used in conjunction with the process for improving the ph sical properties of these alloys by the ad ition of alkali metals to the molten allo as described in the patent of Junius D. dwards, Francis 0. Frary and Harry V. Churchill, No. 1,410,461, issued March 21, 1922, on their application Serial No. 426,796, copending herewith. For example, chill cast test bars of an alloy containing 8 per cent silicon and 10 per cent zinc, to which alkali metals were added before pouring, gave an average tensile strength of over 41,000 poun 5 per square inch and an elongation of 6.2 per cent in 2 inches. Heat-treatment reduced the tensile strength to 34,000 pounds per square inch, but increased the elongation to 14 per cent.

To obtain the best results it is desirable, in all the above mentioned aluminum-silicon alloys, to keep the iron content low, preferably below 0.6 per cent.

It is found that the coarser the grain pro duced in casting, the longer must the heattreatment be continued to produce the most beneficial results. Accordingly sand castings with large cross-sectional areas require longer heating than chill castings. Usually holding at temperature for about 7 hours is suflicient for chill castings, whereas 24 hours may be necessary with sand castings.

In addition to the production of a superior grade of sand castings, permanent mold or chill castin (including die castings), the application o our invention is also most important in connection with the for ing and pressing of aluminum alloys. If it is desired to produce, a forging of a given shape, a casting of suitable composition, say

a 4 per cent copper and 0.2 per cent magnesium, is made, preferably in a chill mold, and is subjected to heat-treatment by our method to produce a starting material for forgin In t is case, instead of quenchin from the heat-treatment temperature and t en reheating the article to forging temperature, we find it preferable to simply cool slowly from the heat-treatment temperature to the forging temperature. The piece is then finished to size under the ress or hammer, after which it is given a s ort heating, say at 520 (1., followed by quenching.

The-duration of the heat-treatment step of our method depends, in large measure, other conditions being the same, upon the degree of improvement desired in the physical properties of the casting.

The essential thing to be kept in mind is the relatively long time required for east alloys in general, as compared to those rolled aluminum-copper alloys known to the prior heat-treating art. This is caused, in the case of the cast copper alloys, by the greater difficulty in etting the unbroken CuAl network into stfiution in the aluminum, and in the case of the silicon alloys by the slowness of change of form of the silicon. In case both copper and silicon are present in substantial quantities, time must be allowed for both of these changes to take place to the extent necessary for the desired improvement. i

In the copper alloys containing about 4 per cent copper, for example, it is found that heating for very long periods, say 48 hours or more, at temperatures only slightly below 500 C. will not, in general, produce as good results as a five hour treatment at 520 C. In chill castings of the copper alloys it has been found that even two hours heating at 520 C. produced substantially as good results as about 22 hours at 500 C. In order to reduce the time to a minimum, we prefer, if suitable temperature control is available, to use as high a temperature as can be safely em loyed without spoiling the castings by over eating.

We have also found that in the case of alloy containing substantial amounts of silicon, the change in shape of the silicon particles is effected more quickly and. more completely at relatively high temperatures. In these alloys, heating for about 12 hours at 520 C. produces very substantial improvement, but the time may be extended, with slight additional improvement, if desired. At a tem erature of 550 to 570 C. the aluminum-Si icon alloys may be heattreated with more beneficial results than can be produced at 500 C. or thereabouts.

It is to beunderstood that the invention is not limited to the specific details herein described but can be practised in other ways without departure from its spirit.

We claim:

1. In the art of making aluminum alloy castings, the method comprising heating an alloy castin containing a substantial amount of sillcon, to a temperature slightly below the melting point of the eutectic, and maintaining. such temperature until the silicon particles have been sufficiently altered in shape to materially improve the physical properties of the cast alloy.

2. In the art of making aluminum alloy castings, the method comprisin preparing an alloy containing a substantia amount of 3. In the art of making aluminum alloy castin the method com rising reparing an al y containing a su stantia amount of silicon, chill casting the alloy whereby the silicon is caused to take the form of relatively small particles in the solidified alloy, heating the casting to a temperature slight y below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufliciently altered in shape to materially improve the physical properties of the alloy.

4. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing from 3 to 15 per cent silicon, to a temperatureslightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufficiently altered in shape to materially improve the physical properties of the cast alloy.

5. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 3 to 15 per cent silicon, casting the 9.110 and causin the silicon therein to take the form of re atively small particles heating the casting to a tempera ture slightly below the meltm point of the eutectic, and maintaining suc temperature until the silicon particles have been sufliciently altered to materially improve the physical roperties of the cast alloy.

6. In t e art of making aluminum alloy castings, the method comprising heating an alloy casting containing from 8 to 10 per cent silicon, to a temperature slightly below the melting point of the eutectic, and maintainin such temperature until the silicon partic es have been sufiiciently altered in shape to materially improve the physical properties of the cast alloy.

7 In the art'of making aluminum alloy castings, the method comprising heating an alloy castin containing a substantial amount of si icon and not more than about 0.6 per cent of iron, to a temperature slightl below the melting point of the eutectic, an maintaining such temperature until the silicon particles have been sufliciently altered in shape to materially improve the physical properties of the cast alloy.

8. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing a substantial amount of silicon, at a temperature slightly below the melting-point of the eutectic until the silicon particles have been sufliciently altered in shape to materially im rove the physical properties of the cast alloy, and ooolirig the casting ra idly.

9. n the art of ma ing aluminum alloy castings, the method comprising preparing an alloy containing a substantial amount of silicon, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting at a temperature slig tly below the melting point of'the eutectic until the silicon particles have been sufliciently altered to materially improve the hysical properties of the cast alloy, and coo ing the castm rapidly.

10.- n t e art of making aluminum alloy castings, the method comprisin preparin an alloy containing a substantia amount 0 silicon, chill casting the alloy whereby the silicon is caused to take the form of relatively small particles in the solidified alloy, heatlng the casting at a temperature slight y below the melting point of the eutectic until the silicon particles have been suificiently altered in shape to materially improve the physical properties of the alloy, and cooling the castin rapidly.

11. In tile art of making aluminum alloy castings, the method comprising heating an alloy casting containing from 3 to 15 per cent silicon, at a tem erature slightly below the melting oint o the eutectic until the silicon partic es have been sufiiciently altered in shape to materially improve the physical properties of the cast alloy, and cooling the castm rapidly.

12. n t e art of making aluminum alloy castings, the method comprising preparing an alloy containing 3 to 15 per cent silicon, casting the allo and causin the silicon therein to take t e form of re atively small particles, heating the castin at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufiiciently altered to materially improve the physical properties of the cast alloy, and

cooling the casting rapidly.

13. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing. from 8 to 10 per cent silicon, at a temperature slightly below the melting oint of the eutectic until the silicon partic es have been sufiiciently altered in shape to materially improve the hysical properties of the cast alloy, and coo ing the castm ra idly.

14-. n t e art of making aluminum alloy castings, the method comprising heating an alloy castin containing a substantial amount of silicon and not more than about 0.6 per cent of iron, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufiiciently altered in shape to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

15. In the art of making aluminum alloy castingathe method comprising heating an alloy casting containing substantial amounts of sllicon and copper, casting the alloy, heatmg the casting to a temperature slightly below the melting poin of the eutectic, and maintaining such temperature until the silicon particles have been sufliciently alteredin shape and a sufficient amount of the intergranular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

16. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing substantial amounts of silicon and copper, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting to a temperature slig tly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufiiciently altered and a suflicient amount of the intergranular copper-rich constituent has been dissolved to materially improve the physical pro erties of the cast alloy.

1?. In the art of making aluminum alloy castin s, the method comprising heating an a oy, casting containing substantial amounts of silicon and copper, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufliciently altered and a suflicient amount of the intergranular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

18. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing substantial amounts of silicon and copper, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting at a temperature slightly below the melting point of the eutectic until the silicon particles have been 'sufliciently altered and a suflicient amount of the interanular copper-rich constituent has been dissolved to materially im rove the physical properties of the cast a loy, and cooling the casting rapidly.

19. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing a substantial amount of copper and 3 to 15 per cent silicon, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufficiently altered in shape and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

20. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing a substantial amount of copper and 3 to 15 per cent silicon, at a temperature slightly below the -melting point of the eutectic until the silicon particles have been sufliciently altered in shape and a suflicient amount of the interranular copper-rich constituent has been issolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidlyf 21. In the art of making aluminum alloy castings, the method comprisin preparing an alloy containing a substantial amount of copper and 3 to 15 per cent silicon, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting to a temperature slightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dlssolved to materially improve the physical properties of the cast alloy.

22. In the art of making aluminum alloy castings, the method comprisin preparing an alloy containing a substantial amount of copper and 3 to 15 per cent silicon, casting the alloy and causin the silicon therein to take the form of relatively small particles in the solidified allo heating the casting at a temperature slig tly below the melting point of the eutectic until the silicon particles have been sufliciently altered and a sufficicnt amount of the inter-granular copperrich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

23. In the. art of making aluminum alloy castings, the method comprising heating an alloy casting containing substantial amounts of silicon and copper and having a low iron content, to a temperature slightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufiiciently altered in shape and a sufiicient amount of the inter-granular copper-rich constituent has vbeen dissolved to materially im rove the physical properties of the cast a lay.

24. In the art of making aluminum alloy castings, the method comprising preparin an alloy containing substantial amounts 0 silicon and copper and having a low iron content, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting-to a temperature slightly below the melting point of the eutectic, and maintaining such temperature 'until the silicon particles have been sufiiciently altered and a suflicient amount of the interanular copper-rich constituent has been issolved to materially improve the physical properties of the cast alloy.

25. In the art of making aluminum alloy castings, the method comprising heating an' con particles have been sufficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the castalloy, and cooling the casting rapidly. i

26. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing substantial amounts of silicon and copper and having a low iron content, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting at a temperature slig tly be low the melting point of the eutectic until the silicon particles have been sufficiently altered and a suflicient amount of the inter nular copper-rich constituent has been issolved to materially im rove the physical properties of the cast alloy, and cooling the castin rapidly.

27. In t e art of making aluminum alloy castings, the method comprising heating an alloy casting containing a substantial amount of copper and 3 to 15 per cent silicon, and having a low iron content, casting the alloy, heatin the casting at a temperature slightly be ow the melting point of the eutectic until the silicon articles have been sufliciently altered an a sufficient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the. physical properties of the cast alloy, and cooling the casting rapidly.

28. In the art of making aluminum alloy castings, the method comprisin preparing an alloy containing'a substantia amount of 7 temperature slightly copper and 3 to 15 per cent silicon, and having a low iron content; casting the alloy and causing the silicon therein to take the term of relatively small particles in the solidified alloy, heating the casting to a below the melting point of the eutectic, and maintaining such temperature until the silicon articles have been sufficiently altered an a sufficient aniount of the inter-granular copper-rich constituent has been dissolved to materially llfiplOVG the physical properties of the cast a o 25 In the art of making aluminum alloy castings, the method comprisin preparing an alloy containing a substantia amount of copper and 3 to 15 per cent silicon, and having a low iron content; casting the alloy and causing the silicon therein to take the form of relatively small particles in the 50- lidified alloy, heatin the castin at a temperature slightly be ow the me ting point of the eutectic until the silicon particles have been-sufficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improvethe physical properties of the cast alloy, and cooling the casting rapidly.

rially im rove the physical properties of A:

the cast a loy.

31. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and a substantial amount of silicon, casting the alloy and causing the silicon therein to takethe form of relatively small particles in the solidified allo heating the casting to a temperature slig tly below the melting point of the eutectic, and maintaining suc temperature until the silicon particles have been suliiciently altered and a sulficient amount of the inter-granular copper-rich constituenthas been dlssolved to materially iilnprove the physical properties of the cast a loy.

32. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 2 to 5.5 or cent copper and a substantial amount 0 silicon, at a temperature slightly below the melting point of the eutectic until the silicon par ticles have been sufiiciently altered and a suflicient amount of the inter-granular copper-richi'constituent has been dissolved to materially improve the physical pro erties of. the cast alloy, and cooling tl ie castin ra idly.

33. n tlie art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and a substantial amount of silicon, casting the alloy and causin the silicon therein to take the form of re atively small particles in the solidified allo heating the casting at a temperature slig tly below the melting point of the eutectic until the silicon particles have been sufliciently altered and a sufiicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, .and cooling the castin ra idly.

34. In t e art of making aluminum alloy castings, the method comprising heating an alloy casting containing 2 to 5.5 per cent copper and 3 to 15 per cent silicon, at a temperature slightly below the melting point of the eutectic until the silicon particles have beensufliciently altered in shape and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

35. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 2 to 5.5 per cent copper and 3 to 15 per cent silicon, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufliciently altered in shape and a sufi'icient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

36. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and 3 to 15 or cent silicon, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting to a temperature slig tly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufliciently altered and a sufficient amount of the interanular copper-rich corstituent has been (Ii ssolved to materially improve the physical properties of the cast alloy.

37. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and 3 to 15 er cent silicon, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting at a temperature slightly below the melting point of the eutectic until the silicon particles have been suificiently altered and a sufiicient amount of the interranular copperrich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

38. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 2 to 5.5 per cent copper and a substantial amount of silicon, and having a low iron content, to a temperature slightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufficiently altered in shape and a sufficient amount of the inter-granular copper-rich constituent has been dissolved to materially lIIIiPIOVB the physical properties of the cast a 0y.

39. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and a substantial amount of silicon, and having a low iron content, casting the alloy, and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting to a temperature slig tly below the melting point of the eutectic. and maintaining such temperature until the silicon particles have been sufficiently altered and a suilicient amount of the inter-granular copper-rich constituent has been dissolved to materially im rove the physical properties of the cast a 0 40. In the art of making aluminum a 0y castings, the method comprising heating an alloy casting containing 2 to 5.5 per cent copper and a substantial amount of silicon, and having a low iron content, casting the alloy, heating the casting at a temperature slightly below the melting oint of the eutectic until the silicon partic es have been sufficiently altered and a sufficient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

41. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and a substantial amount of silicon, and having a low iron content, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting at a temperature slightly below the melting oint of the eutectic until the silicon partic es have been sufiiciently altered and a suificient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

42. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 2 to. 5.5 per cent copper and 3 to 15 per cent silicon, and havin a low iron content, at a temperature slight y below the melting point of the eutectic until the silicon particles have been sufficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting ra idly.

43. In the art of making a uminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and 3 to 15 per cent silicon, and having a low iron content; casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting to a temperature slightl below the melting point of the eutectic, an maintaining such temperature until the silicon particles have been sufliciently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially im- PIiOVe the physical properties of the cast al 0 4% In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 2 to 5.5 per cent copper and 3 to 15 per cent silicon, and having a low iron content; casting the alloy and causing the silicon therein to take the "form of relatively small particles in the solidified alloy, heatin the casting at a temperature slightly low the melting point of the eutectic until the silicon particles have been sufficiently altered and a sufiicient amount of the inter-granular copper-rich constituent has been dissolved to materially im rove the ph sical properties of the cast a 0y, and coo ing the casting rapidly.

45. n the art of making aluminum alloy castings, the method comprising heating an alloy casting containin 3 to 10 per cent silicon and a substantia amount of copper, at a temperature slightly below the melting pointof the eutectic until thesilicon particles have been sufliciently altered in shape and a sulficient amount of the intergranular copper-rich constituents has been dissolved to materially improve the physical properties of the cast alloy.

46. In the art of making aluminum al- 10y castings, the method comprising heating an alloy casting containing 3 to 10 per cent silicon and. a substantial amount of copper, at a temperature slightly below the melting point of the eutectic untilthe silicon particles have been sufficiently altered in shape and a suflicient amount of the interranular copper-rich constituent has been issolved to materially improve the physical properties of the cast alloy, and coo ing the castin ra idly.

47. tile art of making aluminum alloy castings, the method comprising preparing an al 0y containin 3 to 10 per cent silicon and a substantia amount of copper, casting the allo and causin the silicon therein to take t e form of re ativel small particles in the solidified alloy, heating the casting to a temperature slightly below the melting point of the eutectic, and maintaining such'temperature until the silicon particles have been sufliciently altered and a sut'ficient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

48. In the art of making aluminum alloy castin s, the method comprising preparing an al 0y containin 3 to 10 er cent silicon and a substantiaI amount 0 copper, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufliciently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

49. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 3 to 10 r cent silicon and a substantial amount 0 copper, and having an iron content not exceeding about 0.6 per cent, at a temperature slightly below the melting point of the eutectic until the silicon partlcles have been suflicientl altered in'sha e and a suflicient amount 0? the inter-granu ar copper-rich constituent has been dissolved to materially im rove the physical properties of the cast a 0y.

50. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 3 to 10 per cent silicon and a substantial amount of cop er, and having an iron content not excee ing about 0.6 per cent, at a temperature slightly below the meltin point of the eutectic until the silicon par-tic es have been sufficiently altered in sha e and a sufficient amount of the inter-granu ar copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting ra idly.

51. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing?) to 10 per cent silicon and a substantial amount of copper,- and having an iron content not exceeding about 0.6 per cent; casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting to a temperature slightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufiiciently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

52. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 3 to 10 per cent silicon and a substantial amount of co per, and

having an iron content not excee ing about 0.6 per cent; casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting at a temperature slight below the meltin point of the eutectic until the silicon partic es have been sufficiently altered and a sufficient amount of the intergranular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

53. In t e art of making aluminum alloy castings, the method comprising heating an alloy casting containing copper 4 per cent and silicon 6 per cent, approximately, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufiiciently altered in shape and a sufiicient amount of the inter-granular copper-rich constituent has been dissolved to materially im rove the physical properties of the cast al oy.

54. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing 4 per cent copper and 6 per cent silicon, approximately, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufliciently altered in shape and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the hysical properties of the cast alloy, and coo ing the castm ra 'dly.

55. n t e art of making aluminum alloy castings, the method comprising preparingan alloy containing 4 per cent copper and 6 per cent silicon, ap roximately, casting the alloy and causing t e silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting to a temperature slightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical propertiesof the cast alloy.

56. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing 4 per cent copper and 6 per cent silicon, approximately, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufficiently altered and a sufficient amount of the inter-granular copperrich constituent has been (llSSOlVBd to materially improve the physical properties of the cast alloy and cooling the casting rapidly.

57. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing substantial amounts of silicon and copper and a relatively small amount of magnesium, to a temperature slightly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sulficiently altered in shape and a sufficient amount of the inter-granular copper-rich constituent has been dissolved to materially llfipIOVB the physical properties of the cast a oy.

58. In the art of making aluminum alloy castings, the method comprising preparin an alloy containing substantial amounts 0 silicon and copper and a relatively small amount of magnesium, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting to a temperature silg tly below the melting point of the eutectic, and maintaining such temperature until the silicon particles have been sufli; ciently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

59. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing substantial amounts of silicon and copper and a relatively small amount of magnesium, at a temperature slightly below the melting point of the eutectic until the silicon particles have been sulficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

60. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing substantial amounts of silicon and copper and a relatively small amount of magnesium, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified allo heating the casting at a temperature slig tly below the melting point of "the eutectic until the silicon particles have been sufficiently altered and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

61. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing a substantial amount of copper and 3 to 15 per cent silicon, and a relatively small amount of magnesium, casting the alloy, and heating the casting at a temperature slightly below the melting point of the eutectic until the silicon particles have been sufliciently altered in shape and a suflicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

62. In the art of making aluminum alloy castings, the method comprising heating an alloy casting containing a substantial amount of copper and 3 to 15 per cent silicon, and a relatively small amount of magnesium, casting the alloy, heating the casting at a temperature slightly below the melting oint of the eutectic until the silicon partlcles have been sufliciently altered in shape and a suflicient amount of the interranu ar copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling th e casting ra idly.

63. In t e art of making aluminum alloy castin s, the method comprising preparing an al oy containing a substantial amount of copper and 3 to 15 per cent silicon, and a relatively small amount of magnesium, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heating the casting to a temperature slightly below the melting point of the eutectic, and maintainin such temperature until the silicon partic es have been sufliciently altered and a sufficient amount of the interranular copper-rich constituent has been issolved to materially improve the physical properties of the cast alloy. 7

64. In the art of making aluminum alloy castings, the method comprisin preparing an alloy containing a substantia amount of copper and 3 to 15 per cent silicon, and a relatively small amount of ma esium, casting the alloy and causing the silicon therein to take the form of relatively small particles in the solidified alloy, heatin the casting at a temperature slightly low the melting oint of the eutectic until the silicon particles have been sufiiciently altered and a sufiicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the hysical properties of the cast alloy, and coo ing the castm ra id y. i

65. n tlie art of making aluminum alloy castings, the method comprising preparing an alloy containing about 4 per cent copper, magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and silicon in excess 0 the iron, and in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the alloy; heating the casting at a temperature between about 500 C. and about 540 (3., for a relatively long eriod of time, until a sufiicient amount of tlie inter-granular cop per-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

66. In the art of making aluminum. alloy castings, the method comprising preparing an alloy containing about 4 per cent copper, magnesium not exceeding about 0.3 per cent, iron not exceedin about 0.4 per cent, and silicon in excess 0 the iron, and in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the alloy; and heating the casting at a temperature between about 500 (3. and about 540 C. for not less than about two hours, until a. sufficient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

67. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing about 4 per cent copper,

magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and

silicon in excess of the iron, and in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the alloyand causing rapid solidification thereof in the mold; and heating the casting at a temperature between about 500 C. and about 540 (3. for a relatively long period of time, until a sutficient amount of the intergranular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

68. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing about 4 per cent copper, magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and silicon in excess of the iron. and in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the alloy and causing rapid solidification thereof in the mold; and heating the casting at a temperature between about 500 (3. and about 540 C. for not less than about 2 hours, until a sufficient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy.

69. In the art of making aluminum alloy castings, the method comprising preparin an alloy containing 0.25 per cent zinc an 4 per cent copper, approximately, magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and silicon in excess of the iron,'and in preparing the alloy keeping-the temperature not greatly in excess of 750 (3.; casting the allo heating the casting at a temperature etween about 500 C. and about 540 (3., for a relatively long period of time, until a sufiicient amount of the inter-granular copper-rich constituent has been dlssolved to materially improve the physical properties of the cast alloy.

70. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing about 4 per cent copper, magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and

silicon in excess of the iron, and in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the alloy, heating the casting at a temperature between about 500 C. and 540 0., for a relatively long period of time, until a sufiicient amount of the inter-granular copperrich constituent has. been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidly.

71. In the art of making aluminum alloy -castings, the method comprising preparing an alloy containingabout 4 per cent copper, magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and silicon in excess of the iI'011,"8.Dd in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the alloy, heating the casting at a temperature between about 500 (3. andabout 540 (3. for

not less than about 2 hours, until a suflicient amount of the inter-granular cooper-rich constituent has been dissolved to materially improve the physical properties of the cast allay, and cooling the casting rapidly.

72. In the art of making aluminum alloy castings, the method comprising preparing an alloy containing about 4 per cent copper, magnesium not exceeding about 0.3 per cent. iron not exceeding about 0.4: per cent, and silicon in excess of the iron, and in preparing the alloy keeping the temperature not greatly in excess of 750 C. casting the alloy and causing rapid solidification thereof in the mold; heating the casting at a temperature between about 500 C. and about 540 (3., for a relatively long period of time, until a sufticient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting ra idl 1 3. in the art of making aluminum alloy castings, the method comprising preparing an alloy containing about 4 per cent copper, magnesium not exceeding about 0.3 per cent, iron not exceeding about 0.4 per cent, and silicon in excess of the iron, and in preparing the alloy keeping the temperature not greatly in excess of 750 (3.; casting the allo and causing rapid solidification thereof in the mold; heating the casting at a temperature between about 500 C. and about 540 C. for not less than about 2 hours, until a sufiicient amount of the inter-granular copper-rich constituent has been dissolved to materially improve the physical properties of the cast alloy, and cooling the casting rapidlyu 74. As a new article of manufacture, a heat-treated casting of an aluminum alloy containin a substantial amount of silicon, characterized by the silicon being in the form of small finely dispersed more or less rounded particles and substantially devoid of large plates and needles of silicon, with consequent high tensile strength and elongation.

75. As a new article of manufacture, a heat-treated casting of an aluminum alloy containing silicon in amount between 3 and 15 per cent, characterized by the silicon being in the form of small finely dispersed more or less rounded particles and substantially devoid of large plates and needles of silicon, with consequent high tensile strength and elongation.

76. As a new article of manufacture, a heat-treated castingof an aluminum alloy containing substantial amounts of silicon and copper, characterized by the silicon being in the form of small finely dispersed more or less rounded particles and substan' tiall devoid of large silicon plates or nee lcs and of undissolved inter-granular copper-rich constituent, with consequent high tensile strength and elongation.

77. As a new article of manufacture, a heat-treated casting of an aluminum alloy containing a substantial amount of silicon and having a low iron content, characterized by the silicon being in the form of small finely dispersed more or less rounded particles and substantially devoid of large plates and needles of silicon, with consequent high tensile strength and elongation.

78. As a new article of manufacture, a

heat-treated casting of an aluminum alloy containing silicon in amount between 3 and 15 percent and having a low iron content, characterized by the silicon being in the form of small finely dispersed more or less rounded particles and substantially devoid of large silicon plates or needles of silicon, with consequent high tensile strength and elongation.

79. As a new article of manufacture, a heat-treated casting of an aluminum alloy containing substantial amounts of silicon and copper and a relatively small amount of magnesium, and having a low iron content, characterized by the silicon being in the form of small finely dispersed more or less rounded particles and substantially devoid of lar e silicon plates or needles and of undissolved inter-granular copper-rich constituent, with consequent high tensile strength and elongation.

80. As a new article of manufacture, a heat-treated casting of an aluminum alloy containing substantial amounts of silicon and copper and a-relatively small amount of magnesium, characterized by the silicon being in the form of small finely dispersed more or 1cm rounded particles and substantiall devoid of large silicon plates or nee es and of undissolved inter-granular co er-rich constituent, with consequent big tensile strengfih and elongation.

n testimony w ereof we hereto afiix our signatures.

ZAY JEFFRIES. ROBERT S. ARCHER.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,508,556., ranted September 16, 1924, upon the apglication of Zay Jefleries, of Cleveland ei hts and Robert S. Archer, of East Cleveland, Ohio, for an improvement in akmg Castings of Aluminum AlIoys,-errors appear in the prmted specification requiring correction as follows: Page 6, lines 127 and 128, claim 15; age 8, lines 26 and 27, claim 27; page 9, lines 74 and 75, claim 40, and page 11, ines 116 and 117, claim 62, strike out the words cast-ingthe alloy, heating the casting; age 11, lines 103 and 10-1, claim 61, strike out the words casting the qlloy, ans heating the casting ahd that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the cas in the Patent Office.

Signed and sealed this 28th day ofApzil, A. D. 1925.