US2290019A - Aluminum alloy - Google Patents

Description

Patented July 14, 1942 2,290,019 ALUMINUMUALLOY Walter Bonsack, South Euclid, Ohio, assignor to The National smelting Company, Cleveland,

Ohioya corporation of Ohio No Drawing. Application June 28, 1941,

. Serial No. 400,327

6 Claims. (C l- 75- 146) This. invention relates to alloys, and particularly to aluminum base alloys suitable for casting and working and having' high strength at ordinary and elevated temperatures.

This application is a division of my copending application Serial No. 389,020, filed April 17, 1941, for Aluminum alloys.

It is an object of this invention to produce alloys having relatively high elongation and relatively high tensile strength.

It is a further object of this invention to provide a relatively light alloy which may be easily cast and machined, which may be used at elevated temperatures without a rapid deterioration formulas and, for the purpose of theimproved alloy, the magnesium'and zinc should be present in about the proportion necessary to form, the

ternary compound of either formula.

An excess of zinc, over and above that which cooperates with magnesium and aluminum to form a ternary compound according to the above formula having the greatest proportion of zinc,

increases the brittleness and decreases the ductility of the alloy. For this reason it is undesirable that zinc be present in quantities substantially greater than the amount to react to form such a ternary compound with magnesium'and aluminum. The most desirable properties are obtained when the magnesium and the zinc are of desirable properties, and hich may b readily l5. proportioned so that the ratio of magnesium (untreated with anodic treatment to give excellent combined with any s o to Zinc is about equal lustre and finish. to the ratio represented .by the formula It is astill further object of this invention to AliMgazna, or somewh larger as represented by provide an alloy having a relatively. high proporthe formula AlsMgvZnc. .A small amount of magtional limit and relatively high fatigue strength, nesium may be provided to replenish losses that and in which these properties may be obtai d may occur when the alloy metal is remelted. without heat treatment. Magnesium adds to the hardness and machin It has been found that an aluminum alloy ing qualities of the alloy and, as above .stated, containing iron,- and having zinc and magnesium should be present in an amount suflicient to compresent in proper proportions, will produce an bine with the zinc and .aluminum present. In alloy that may be readily cast and have improved greater quantities, magnesium tends to make the physical properties for use both at ordinary alloy sluggish, dec ea castabilityand elevated temperatures, and which may have M es um d z a heretofore been these properties improved by heat treatment. ed o aluminum in the proportion r s d When magnesium and zinc are added to alumiby the fo u Mgzm- It has been found. W- num in the proper proportions, a, ternary ever, that a given percentage of ternary compound of aluminum, magnesium and zi c i pound is more effective in producing desirable formed, which compound is soluble in solid solu- Properties, and because the inc Content of the tion in the aluminum. The presence of this comt rnary alloys s .less y v a lower s pound in relatively small amounts greatly im- 5 T e improved aluminum alloys may have the proves the characteristics of aluminum and prot tern ry p u of aluminum, Zinc and duces an alloy having high strength combined n s um p s nt n an am u t ranging from about with high ductility, good casting and forging to 20%, e preferred nge bein between properties, good color and excellent corrosion re- 0ut 3% and 15%. At room temp the tele sistance. In calculating the a t of magnary compound goes into solid solution in aluminesium and zinc that should be present in the num alloys in an amount of about /0- 'h D aluminum alloy to form 'the desired percentage centage in solid solution increases at high temof ternary compound, only magnesium which i peratures and decreases uponcooling, the excess not combined with silicon is to be calculated, as precipitating ou Aluminum. alloys containing it is only such magnesiumthat is available to the e n y compound thereforebe advancombine with zinc and aluminum to form the tageously heat treated to improve their properternary compound. ties.

The ternary compound is said'by some lnvesti- A small amount/of silicon is usually present gators to have a composition having substantially in aluminum-alloys and from 15% to about 31% the formula AlsMgvZm, and other investigators 5 is desirable in alloys of the present invention have considered the formula for the ternary which are to be forged or drawnymore than 37% I compound as being AlzMgszm. It will 'be seen is frequently desirable in casting alloys. Silicon that the amounts of magnesium and zinc relacombines with magnesium in preference to most tive to each other are quite similar in both elements, each part by weight of silicon combining with about 1.75%, by weight of magnesium zinc and form the ternary compound according to the formula AlzMgaZna. MgzSi is more stable than the ternary compound above mentioned and may be maintained in solid solution in aluminum alloys in an amount up to about 1.85%, which is the quantity of MgzSi present if the silicon is present in the alloy, and acts as a hardener which is sometimes desirable in conjunction with the ternary compound. MgzSi does not, however, make as eflicient use of the magnesium as'does the above mentioned temary compound. Therefore, it is desirable to have the magnesium present on the rich side to prevent the silicon from being present in excess and taking magnesium away from the ternary compound.

If the alloy is desired particularly for casting 2 purposes ,'more silicon, such as up to about 1.5%, may be present. If however a somewhat larger amount of silicon is present in the alloy than is desirable for the purpose for which the alloy is intended, and such amount of silicon is not too excessive, then a small amount of calcium may be added. Calcium has an even stronger aiiinity for silicon than has magnesium and, therefore, it can be used to reduce the amount of silicon available for combination with magnesium. The amount of the relatively expensive magnesium available for the formation of the ternary compound may thus be increased. Althrough much more than 1.85% silicide acts as a supplemental hardener and more than about a 3% or makes the alloy more sluggish and adversely affects the castability of the alloy, up to 3% is desirableand more than 3% may in some cases be desirable in the production of hard castings having less intricate shapes, par- 40 ticularly when a large amount of the ternary compound is present in the alloy. Usually, however, the amount of silicon should be between .5%' and 1.5%, especially in castings not heat treated. This is true even when calcium is pres- 4.1 ent, although with the latter element more magnesium is available for formation of the ternary compound.

It has now been found that aluminum alloys containing magnesium (over that necessary to combine with silicon) and zinc in the proportions to form a ternary compound are greatly improved by the addition of one or more members of the group of hardening elements, ,con-

sisting or .1%to 1.5% nickel, .1% to 1.5% manrm ganese and .05% to 1% chromium in a total amount of about .2% or .3% to 5%, with or without one or more of the grain refining elements selected from the group consisting of titanium,

columbium, zirconium boron, tungsten, molyb- 6 denum, tantalum and vanadium in a total amount of .005% to .5%.

Although the metals manganese, chromium and nickel each increase the hardness of thealloy, a given percentage of each of these elements improves certain of the properties more than it does others. It is therefore preferred that more than one of these elements be present in the alloy. Nickel increasesthe tensile strength, proportional limit and yield strength of the alloy without decreasing its elongation to any appreciable'degree. In fact, with certain amounts of nickel the elongation is increased, so that an alloy having exceedingly desirable and exceptional properties may be'obtained.

Alloys containing nickel may be readily heat treated or age hardened to. give somewhat superior properties, but very desirable properties which are almost equivalent to the heat treated alloys are also obtained when castings are simply aged at room temperature, with or without quenching from the mold.

Nickel is quite an effective element in the alloy and appreciable improvements in properties of the alloy are noted when it is present in an amount of about .1%, or more. The preferred properties are obtained with about .3% to about .8% or 1% nickel, and in some cases it is desirable to have the nickel present in amounts as great as 1.5%.

Manganese, although it decreases the tensile strength and elongation to some degree, increases the yield strength, hardness and proportional limit of the alloy. It also makes the alloy more corrosion resistant.

Alloys containing manganese may be readily heat treated or age hardened to give somewhat superior properties, but very desirable properties are obtainable when castings are simply aged at room temperature, or when quenched from the mold and aged.

Manganese is a very eifective element in they alloy and desirable improvements are noted when about .1%, or even a little less, is present in the alloy. The preferred properties are obtained withabout .2% to about .5% or .8% manganese, and in some cases it is desirable to have the manganese present in amounts as great as about 1%, or even 1.5%.

Chromium, although it does not appear to improve the proportional limit and yield strength of the alloy, increases its elongation. It is, therefore, particularly advantageous that both chromium and manganese be present. As little as .05% or .1% chromium, particularly with manganese, is effective in improving properties of the alloy, but .2% or .3% to about .8% or even 1% is desirable. When manganese is also present, the total of manganese and chromium should preferably be between about .3% and 1.5% ofthe alloy. When both manganese and chromium are present, they may be in about equal proportions, or preferably with a slightly greater amount of manganese than chromium.

The quantity of each of the hardening metals desired in a given alloy also depends somewhat upon the quantity of other hardening ingredients present and upon the amount of ternary compound, a given hardness and tensile strength often being obtainable either with a relatively large amount of strength-improving hardening metal and a relatively small amount of ternary compound, or with a relatively small amount of such metal and a relatively large amount of magnesium and zinc in the proportions of a ternary compound.

, As silicon decreases the ductility of the alloy to a substantial degree, it is best that when thealloy contains nickel present in the upper portion of the above mentioned range that the silicon does not exceed .'7% or .8%, as the presence of too much oLthe hardener MgzSl may decrease tent, alloys containing such low percentages of a ternar compound are relatively, diflicult to cast.

An alloy'containing 2% of the ternary compound may be used for casting purposes; The castability, however, is improved with an increase in the amount of ternary compound and it is, therefore, preferred to have a larger percentage of the ternary compound present, such as 4% to 8% for casting purposes. When the casting is more or less intricately shaped,-still greater percentages, such as 10% to or of the ternary compound may be present. For alloys to be forged, or shaped after casting, the ternary. compound should be present in the lower ranges, such as 2% .or 8% or so, as the metal is less hard with the lower percentages of the ternary compound.

A larger proportion of the ternary compound and metals of the above hardening group may be ternary present, a given hardness and tensile strength often being obtainable with a relatively larger amount of iron and a relatively smaller exert a still further improvement independently if iron.

The aluminum alloys of the present invention containing magnesium, uncombined with silicon,

and zinc in the proportion of a ternary com- I pound, when cast in .molds of a design such that obtained when they contain the ternary compound in amounts up to 20% or so, whereas less of the ternary compound, such as 4% to 15%, is preferred in alloys which are quenched upon removal from-the mold and heat treated at a low temperature, or aged at room temperature.

It has generally been considered that aluminum alloys of magnesium containing iron much above the impurity value in commercial aluminum are 'of little commercial value; but it has also now been found that an alloy containing the above described ternary compound, with or without one or more of the above mentioned group of hardening elements, and with or without one or more of the above group of grain refiners, is

improved by the presence of iron in suitable proportion. I

Iron in suitable amounts further increases the hardness and tensile strength of the alloy without decreasing its ductility a substantial amount. A small amount of iron thus permits one to obtain the properties desired .with a smaller amount of magnesium and zinc. These alloys chilling takes place substantially simultaneously in the various portions of the casting, solidify without the use of grain refining agents and form good castings. However, it has been found that certain grain refining elements substantially improve the properties of the aluminum alloy containing the ternary compound, whether or not it contains one or more of the above hard- ,ening metals, with or without iron. This is especially true when the metal is .cast in molds of more or less intricate shape where the chilling may not be so uniform throughout the casting.

The grain refiners which I have found improve the properties of the alloy are members of the group consisting of boron in the amount of .005%

to .1%, zirconium in the amount of .01% to .5%, tungsten in the amount of .01% t0 .5%,

molybdenum in the amount of .01% 'to .5%,

vanadium in the amount of .01% to 5%, titanium in the amount of .05% 'to .5%, columbium in the amount of .01% to .5% and tantalum in the amount of .05% to .5%. These grain refining elements should preferably be present in' a total amount of from .005% to .5% and it isfrei quently desirable to have more than one ofthese elements present in a given alloy.

While the grain refiners in the above group are desirable in the alloys of the present invention, not all of the grain refiners affect'the properties in the same way. The particular refiner tiO containing iron may be readily' heat treated or age hardened to give somewhat superior properties, but the iron in combination with the ternary elements in the above pro'portion'is also outstanding in that almost as desirable properties are obtained when castings are aged at room temperature without a heat treatment or quenching. i i

Iron has generally been considered to crystallize in large platelike crystals, which weaken the alloy. Iron in" the presence of the ternary compound appears to crystallize in finely dispersed form, and the ternary compound also seems to be dispersed, thus producing a highly desirable alloy.

Iron in the amount of .4% or more in the alloys of the present invention gives noticeable or group'of refiners selected in any given inlected from the group consisting of titanium, tungsten, molybdenum, zirconium and vanadium, and especially tungsten and molybdenum, improve both the strength and the elongation of the castings. Of these; titanium being less expensive is usuall used for ordinary castings, but in cases where the highest elongation together with strength is necessary, it is preferred to use tungsten or molybdenum. The grain refiners selected from the group consisting of boron, columbium and tantalum do not appear to appreciably increase the strength or elongation of the alloy and are usually used where appearance, finish and corrosion resistance are most important and where strength is of less consequence. Certain grain refiners, such as cerium, were found to be relatively undesirable-in the alloy.

The above described hardening elements, manganese, chromium and nickel, substantially decrease the hot shortness, improve the properties of the alloy and assist in maintaining the improved properties at high temperatures such as are encountered in internal combustion engines. The above grain refining elements, parof about 7.2%.

therefore, especially desirable to have up to .5%

or so of these latter elements present when other hardening ingredients are absent.

EXAMPLE 1 An aluminum base alloy containing free magnesium and zinc in the proportions represented by about 6% of the ternary compound AlsMg-lzns, about .2% silicon, about .4% nickel, about .6% iron and about .2% titanium was chill cast into test bars, which were quenched from a mold and aged seven days at room temperature. When tested, the test bars had a tensile strength of about 42,500 lbs/sq. in., an elongation of about 10.9%, a Rockwell E hardness of about 80, a proportional limit of about 17,900 lbs/sq. in., and a yield strength of about 23,900 lbs/sq. in.

When the test bars were simply air cooled and aged seven days at room temperature, the tensile strength was 40,700 lbs/sq. in., the elongation was 8.4%, the Rockwell E hardness was 81, the

-t1cularly members of the group consisting of EXAMPLE 4 An aluminum base alloy containing about chromium, about .3% manganese, about .2% silicon, about 3.6% -zinc, and magnesium in suificient amount to combine with the silicon to form Mg2 Si and to form with the zinc and part 01'. the aluminum about 6% of the ternary com-.

EXAMPLE 5 Test bars of an alloy similar to that of Example 4, difiering only in that it. did not contain appreciable quantities of manganese and chromium, were aged 3 hrs. at 125 0., and, when tested, showed a tensile strength of 35,700 lbs/sq. in., a yield strength: of 22,200 1bs./sq. in., a proportional limit of 14,200 lbs./sq.' in., an elongaproportional limit was 18,600 lbs/sq. in., and

the yield strength was 24,100 lbs/sq. in.

EXAMPLE 2 A similar alloy to that of Example 1, containing' only about .25% nickel but having the same .percentage of the other ingredients, was chill cast into test bars, air cooled and aged seven days at room temperature. The test bars had a tensile strength of about 38,400 lbs./sq. in., 'a yield strength of about 23,200 lbs/sq. in., a proportional limit of about 17,700 lbs/sq. in., a hardness of about 82 Rockwell E, and an elongation EXAMPLE 3 An alloy containing about 1.2% nickel, about .3% silicon and about 6% .of the ternary compound was chill cast into test bars, air cooled and aged seven days at room temperature. When tested, the bars had a tensile strength of about 38,600 lbs/sq. in., a yield strength of 25,700 lbs./sq. in., a proportional limit of about -19,200 lbs./sq. in., an elongation of about 5%, anda hardness of about 83 Rockwell E.

From the above examples it is seen that nickel markedly improvedthe hardness, proportional limit, tensile strength and even the elongation I of the alloy. Since most alloying elements which tend to improve the tensile strength of an alloy also usually decrease its elongation to a marked degree, it is seen that nickel in combination with a ternary coinpoundhas a remarkable effeot and that an alloy of outstanding characteristics is produced.

When the quantity of ternary compound is increased, the high tensile strength of the alloy inEXample 1 may be obtained with a somewhat increased tion of about 12.7%, and a hardness of 68 kg./mm

EXAMPLE 6 Test bars chill cast from an, alloy containing 6% of the ternary compound, about .6% iron, about 25% chromium, and about .5% manganese showed, after quenching and aging for seven days at room temperature, a tensile strength of 41,600 lbs/sq. in., a yield strength of 23,500 lbs/sq. in., a proportional limit of 17,600 lbs/sq. in., an elongation of 9.6%, and a hardness of 80 Ira/mm.

When bars of the same alloy were simply air cooled and aged for seven days at room temper.- ature, the tensile strength was 41,600 lbs./sq. in., the yield strength was 23,500 lbs./sq. the proportional limit was 18,100 lbs./sq. in., the elongation was about 8%, and the hardness was 82 When the quantity of manganese in the alloy of Example 6 was increased to about 1%, the tensile strength of air cooled test bars, aged for seven days at room temperature, was 38,900 lbs/sq. in., the yield strength was 26,600 lbs/sq. in., the proportional limit was 20,100 lbs/sq. in., the elongation was about 5%, and the hardness was 82 kg./mm

From the above examples it is seen that even a small proportion of manganese and chromium markedly increases the tensile strength, proportional limit, yield strength, hardness, and even the elongation of aluminum base alloys. Since most alloying elements which tend to improve the tensile strength of an alloyalso usually de- ,crease its elongation to a marked degree, it is seen that manganese and chromium in combin. tion with each other and with a ternary compound have a remarkable efiect, and that an alloy of outstanding characteristics is produced.

An aluminum base alloy containing .2% 111.

- con and magnesium (uncombi'ned with silicon) and zinc in the proportions represented by the tormula AlaMgvZne, and in sufficient amounts to produce 6% of this ternary compound in the alloy, was prepared. From this base alloy three diflerent alloys were prepared by incorporating the proportions of iron indicated in the following Table 1, and chill cast in standard test bar molds. Several bars of each alloy were given-the indicated heat treatments, that is, some of the bars of each alloy were removed fromthe mold,

while hot and allowed to cool in air and then aged seven days at room temperature; another 'set'of bars was removed .from the mold before the bars had cooled sufficiently to precipitate the hardenproportional limit of 18,600 lbs/sqin., a harding ingredients, then quenched in water and allowed to age at room temperature for seven days.

Table 1 Propor- Elonga- Yield Tensile Bnnell AHOY 6 tion strength strength hardness Per cent Percent Lbs/in. Liza/in. Lbalin. KgJ'm'mJ 1' .81 0.2 10, 100 23,300 30.000 -70 22.-.- 1.34 4.4 10, 20,400 30,000 as 3'-.." 1.37 5.4 18,500 25,300 30,000 04 1'2. .81 7.0 10,400 23,100 30,400 70' 2". 1. a4 5.0 10. 400 20,000 41,100 as 0 1.87 5.3 17,400 25,000 40,400 03 Alloy air cooled: agedat room temperature seven days. Alloy quenched; aged at room temperature seven days.

It is seen from the test results of the above table that although the tensile strength may be increased to some extent by a quenching treatment, almost equal results are obtained by simply air cooling the casting and aging it at roomtemperature. Before the quenched. casting is aged,

a tensile strength of over 30,000lbs.-/sq. in. is obtained, while at the'same time the casting has an elongation of 12%. In an aged casting a tensile strength of even greater than 40,000

lbs/sq. in., togetherwith an elongation of almost 8% are obtained. In an aged casting maximum elongation and substantially maximum strength are obtained when the iron content is about 1% or so.

When the quantity of ternary compound is increased, these maximum values may be obtained with a somewhat/lower iron content, or higher maximum strength is obtained with the same ness of about 82 Rockwell E, and an elongation of about 5.7%. When the bars were simply air cooled and aged as above, the tensile strength was 37,700 lbs/sq. in., the yield strength was 25,000 lbs/sq. in., the proportional limit was 19,200 lbs/sq. in., the hardness was 81, and the elongation was 4.5%.

Exempt: 8

hardness of about 81 Rockwell E, and an elongation of 7.8%

EXAMPLE 9 An aluminum base alloy containing about .6

iron, about .3%manganese, about .2% chromium,

about .2% titanium, about .2% silicon,'and magnesium in proportion to combine with the silicon and to form 6% of the ternary compound AlaMmZna with the balance substantially aluminum and minor impurities, was prepared and chill cast into test bars, quenched and aged seven days at room temperature. When tested they showed 9.

iron content; the castability of the alloy may be also somewhat increased. It will be seen that, since'the iron permits one to obtain exceptionally high elongation, combined with high tensile strength, without the necessity of even as much heat treatment as quenching from the mold, the alloy is especially useful for many purposes, such as large castings or forgings, wherein it is diflicult to heat treat or quench.

As shown above, iron and the ternary comaluminum base alloy, with, or without the usual impurities. Even more desirable properties,.for some purposes, are obtained with iron and one or more hardening metals of the group consi .1g of'about-.1% to 1.5% chromium, about .05% to 1.5% manganese, and about .1% to 1.5% nickel. As little as a total of about .1% or .2% of these hardening metals is effective in improving the iron ternary aluminum alloy, but about .4% or pound alone produce exceptional propertiesin an tensile strength of 42,300 lbs/sq. in., an elongation of 10.3%, a yield strength of 24,300 1bs./sq. in., a proportional limit of 18,100 lbs/sq. in., and a Rockwell hardness of 81. When the castings were simply air cooled and aged seven days at room temperature, the tensile strength was 41,000 lbs/sq. in., the yield strength was 24,500 lbs/sq. in., the proportional limit was 19,900, lbs/sq. in., the hardness was 80 Rockwell E, and

' the elongation was 8.5%.

, EXAMPLE 10 An aluminum base alloy containing about .45%

manganese, about .6% iron, about .15% silicon,

. were quenched from the mold and aged at room lbs/sq. in., a hardness of about 81 Rockwell 5% to about 1.5% of these hardening metals is preferred, and even 2% is desirable for many applications. The iron may be present in the amounts above set forth,'but less than about 1.5% is preferred.

The following examples illustrate the effect of these elements onan alloy containing iron.

Exaurn: 7

temperature for seven days. When tested, the bars showed a tensile strength of about 39,800 lbs/sq. in., a proportional limit of about 17,100 lbs/sq. in., a yield strength of about 23,200

and an elongation of about 7.9%. I

Exmru: 11

a tensile strength of about 37,500 lbs/sq.- in., a

proportional limit of about 18,400 lbs/sq. in.,- a yield strength of about 25,700 1bs./sq.in., a hardness of about 83 Rockwell E, and an elongation of about 4.2%.

Exmrui 12 An alloy containing about 55% manganese,

about 2% titanium, about 6% oi. the ternary compound based on the formula AlaMgrZno', and small percentages of iron and silicon was prepared and chill cast into test bars .of standard shape. The test bars were quenched from the mold and aged at room temperature for seven days. The bars, when tested, showed an-elongation or=about 6.8%, a proportional limit 01' about 18,000 lbs/sq. in., a yield strength of about 24,300 lbs./sq. in., a tensile strength of about Rockwell E. v v

The alloys of the above examples containing haveexcellent corrosion resistance and, as seen from-the, above, almost as desirable properties are obtained when they are not quenched from the mold, but simply Wed at room temperature, as when the-alloy is quenched and aged. Exnlr1.s.13

An aluminum base alloy containing magneslum uncombined with silicon and zinc in prothe ternary'compound 01 aluminum, magnesium and zincaccordingto the formula and containing about 2% oi the grain refiner,

. is omitted, the tensile strength and elongation 39,200 lbs/sq. in.,snd a of about 82 elongation of 13%,and a hardness of 79 well E.

When the grain refiner in the above example are lower and the castability is decreased.

Exmnn 17.

When the alloy of Example 16 contained 03% vanadium instead of tungsten, the test bars which were chill cast, quenched and aged seven days at room temperature had a hardness of 74, an elongation 018.7%, a proportional limit 01" 16,500 lbs./sq. in., a yield strength of 24,900 lbs./sq. in., and a tensile strength 01' 38,800 lbs./sq. in. When the percentage oi vanadium was increased to the hardness was 80, the

elongation was 8.5%; the proportional limit was portions to form about -.2% silicon, about 6% of titanium,,was chill cast into test bars which were removed from the mold before they reached precipitation temperature, quenched in water and aged .seven days at room temperature. These bars, when tested, had a tensile strength ,01 "39,800 lbs/sq. in., a yield strength 0! 22,500 lbs./sq. in., a proportional limit of 17,000 lbs./sq in., an

elongation of 9.2% and a hardness of. 79.

Exams: 14

.An jaluminum base alloy like that oi Example 13,- except that it contained 1% iron, and-containing about 2% otrthe grain refiner, titanium, 1 was chillcastinto test bars,which were removed froml the mold befo'reftheyreachcd precipitation temperature, quenched in water and aged seven days atroom temperature.- These bars, when base.alloy .,containing about 3% silicon, about 6% iron, fabout'GVej-of the .above".

ternary comp und, and; about 05% a columbium, was intoG-test bars, which were air cooledand asedseven days at room tem- ,55

perature. When tested, these bars had a tensile strength of 36,100 lbs./sq. in., a'yield strength of 21,700 lbs/sq. in., aproportlonal limit of 16,400 lbsJsq; in;, anelongation of 7.5%, a hardness of grain structure; v murals An aluminum basealloy containing about 6% oi the ternary compound, about .3% manganese, about chromium, about .2% silicon, and

about 8%. tungsten was chill cast into test bars which were quenched and aged three hours at 77, and Mine 17,700 lbs/sq. in., the yield strength was 25,500

lbs./sq.' in., and

the tensile strength was 40,400 lbs./sq. in. Exmru .18

When in the euo of Example 16 the tungsten was substituted by 106% molybdenum, the elongation oi the test bars which were chill cast,

When the molybdenum was increased to .12%,

test bars which were chillv cast, quenched and aged seven days at roomtemperature had an 1 elongation or 12.4%, a proportional limit of 16,700

' lbs/sq. in., a yield strengthoi"24,500 lbs/sq. in.,

. perature was 12.6%; the tensile strength was and atensile strength oi 41,400 lbs./sq. in.

Exnrru: 18a When in the alloy r Example ,16 .05% zircomm was used instead oi the tungsten, the elongation of the test bars which were chill cast,-

quenched and aged seven days at-room tem- 42,300 lbs/sq. in., the yield strengthiwas 26,000

125' C. When tested, these barshad a tensile strength 0140,600 lbs/sq. in., a yield strength 0125300 lbs./sq.in.,a proportional. limit'ot 16,500 ,Iba/sq. andan'elongation of 13.2%, and 1 "a hardness otflfiRbckwell E; When the chill cast j barswerequenchedand-aged seven-days'atiroom 1 temperature, they had a tensile-strength of 48,300

lbs./s;q. in., a yield strength 01126500 lbs./sq.

lbs/sq. in., the proportional limit .was 17,600. -lbs./sq; in., and thehardnessiwas Rockwell E.

Since the molecular proportion. ofzinc is never more than the molecular proportion of the relatively light magnesium in the temarycompound,

it is seen that in addition tohighstrength the I alloys are light inyeight and are, therefore, especially adapted to aircraft: construction and the like. This is particularly true when the quantity of ternary compound is sumciently low so that the'alloy may be structural members.

If the alloy contains uncombined silicon, about 1.75% magnesium ,is required to combine with each percent 01' uncombined silicon to form magnesium silicide (MgzSi) before,any ternary compound will be formed. For example, if 2% of the ternary compound on the basis of AlzMgsZni be desired in an alloy having .396 silicon, the amount of magnesium to be added to form the ternary compound will be .45%. or about .596,

in.,.a proportional limit oi. 18,400 1bs./sqin., 'an '5 7 and the magnesium'to combine with .396 silicon will be about .5%,making a totaloi' about1%.

The magnesium and zinc in an alloy'containing 3%: free silicon and 20% AlsMg-xzns would beabout 796' and 12%, respectively. ,The alloys described herein include aluminum, magnesium and zinc, the zinc being present in the amounts of drawn or rolled into for m 1.2% to 12% of the alloy, and the magnesium, uncombined with silicon, being proportioned to the zinc in the ranges of the formulas given for the ternary compound. The proportions for the formation of the ternary compound in the alloy exist when the magnesium is about 35% to 45% of the zinc content plus 175% of the silicon content. Most desirable properties may be obtained when the magnesium (uncombined with silicon) is in the lowerlpor'tion of this range, or about 35% to 40% of the zinc.

In the above examples of alloys of the present invention it is to be noted that excellent tensile strength and hardness are obtainable ina relatively short time by aging'at room temperature. A very astounding fact has been discovered, however, in connection with these alloys, namely, that the tensile strength may increase up to approximately 50% of its initial value by aging at room temperature for relatively longperiods of time, such as a few months; The same improvement in tensile strength can, of course, be obtained.

relatively quickly by aging at temperatures above room temperature.

The improvement of properties is illustrated by the following table showing the improvement in an alloy containing a small percentageofsilicon,

It is to be understood that in considering the amount of zinc and magnesium to add to aluminum alloys to form the ternary compound of alu- I minum, magnesium and zinc in the alloy, such magnesium as is necessary to combine with the uncombined silicon is not to be considered as part of the magnesium necessary to form the specified amount of ternary compound,

My copending application Serial No. 389,020 and related copending applications are directed to an alloy similar in, composition to that claimed herein, but containing copper, which functionsin a somewhat different manner than do the hardfining r grain refining metalsincluded in this application. Due to the fact that copper is considerably more soluble at high temperatures than at low, it acts as a precipitation ingredient, so

. that articles made from alloys containing it are about 6% ternary compound, about 1% iron, and about .2% titanium. The test bars were chill cast, '-quenched from the mold, and tested after aging at room temperature for the period indi To obtain these exceptional properties in aluminum-base alleys commonly in use one hasto' resort to-a solution and aging heat treatment,

whereas in alloysof the present invention it is not necessary to solution heat treat for improvement in properties.

benefited more by solution heat treatment.

- In the present application, on the other hand,

the constituents have considerably less solid solubility at higher temperatures, and yet give excellent strengths and ductility without solution heat treatment.

It is to be understood that theparticular compounds disclosed and the procedure set forth are presented for purposes of explanation and illustration, and that various equivalents can be used,

and modifications of said procedure can be made without departing from my invention as defined in the appended claims. i

What I claim is:

1. Analuminum alloy containing magnesium, zinc, silicon in amount up to 1.5%, and one or more metals of the hardeners and grain refiners to increase strength, ductility or hardness of the alloy, with the balance. substantially all aluminum and minor impurities, the amount of zinc in the alloy being about -1.2'% to 12%, and the amount or magnesium in the alloy uncombined with the silicon being about 35% to of the 'zinc content, the total magnesiumbeing within the range of about .5% to 7%.

2. An aluminum alloy containing magnesium.

zinc, silicon in amount upv to 1.5%, and one or more metals or the hardeners and grain refiners to increase strength, ductility or hardness of the alloy, no one of such metals being present in The alloys 0! the present invention have good fatigue and tensile strength and a relatively highproportional limit, even at relatively high '1.

temperatures; they may be heat treated to improve and modify their properties; and they have sumcient ductility and. hardness so that they can be used as sheets, rods, wire, structural shapes, castings, machine parts, etc. These ale loys have a desirable color, high corrosion resistance. and may be anodically finished or highly polished with excellent results. and are suitable for many uses, among them being the production of castings which are shaped or iormedto some extent after casting. The alloys having the lower percentages of ternary compound may even be forged at room temperature and are thus useful amounts more than 1.5%, with'the balance sub .stantially. all aluminum and minor impurities,

the amount of zinc in the alloy being about 1.2%

to 12%, and the amount of magnesium inthe alloy uncombined with the silicon being about 35% to 45% or the zinc content, the total magnesium being within the ranse or about .5% to 7%.

3. The alloy set forth in claim 1 in which the zinc content is about 1.2% to 8% and the magnesium content is within the range "oi! about .5% to 6%. i

4. The alloy set iorth in-claim 1 in which the zinc content is about 1.2% to 4.8% and the mag.

nesium content is within the range of about .5%

5. The filloy set forth in claim 1 in which manganese is presentin the amount of about .1% to in which nickel 6. The alloy set iorthin claim 1 is present in the amount of about .1% to 1.5%.

. 1 war-Tim nonsacx. 1