US2045243A - Alloy - Google Patents

Description

Patented June 23, 1936 ALLOY Roy E. Paine, Oakland, Calif., assignor, by mesne assignments, ,to Magnesium Development Corporation, a corporation of Delaware No Drawing. Original application October 4,

1933, Serial No. 692,135. Divided and this application-November 15, 1935, Serial No. 49,967

2 Clai s. .(Cl.75168) The invention relatestomagnesium-base alloys, preferred casting alloys are those contamm and is directed to the development of alloys .of this class which have good corrosion resistance,

particularly in the cast and in the cast and heat promise must quite frequently .be made in order to approach in one alloy the'optimum properties for a given application. For example, it maybe found that corrosion resistance can be sacrificedso to acertain extent to obtain higher tensile strength, yield point,,hardness, or similar mechanical properties. Again, tensile strength may be sacrificed in order to obtain proper casting.

or working characteristics. It is an object of the present invention to develop magnesium alloys to improvement by heat treatment and -adapt-- vision of magnesium-base alloys characterized by,

'good corrosion resistance in either the cast. or in the cast and heat treated condition. A further object is the provision of magnesium alloys pos- I I have discovered that magnesium-base alloys containing from 0.5 per cent. to 22 per cent of lead possess to an appreciable degree the collective characteristicsof alloys which are re sistant to corrosion, alloys which may be readily cast,- alloys which are susceptible" to alteration of properties by thermal treatments, alloys having favorable mechanical properties, and alloys which, within a restricted range, may be worked by extrusion, forging, or other means of mechanical deformation. I

In accordance with my invention leadmay be present in amounts as low as 0.5 per cent.- The above about 5 per cent oi lead since it is in these alloys that the most pronounced combination of these different properties is obtained. The alloy may be worked by extrusion over a range offrom about 0.5 per cent to about 22.0 per cent. 'oilead. As an all around casting alloy I have found amagnesium alloy containing 5 to 10 per cent of lead to be particularly adapted to general foundry purposes. Alloys falling within this preferred range of'co'mposition as well as other alloys comprised within the broader limits previously defined, have been subjected to severe tests designed to produce accelerated corrosion. -Sand cast test bars poured in accordance" with'the best casting practice in the art were subjected to cor-' rosion tests in the as cast and in the heat treated condition. In the example referred to the heat treatment was carried out at about 459 centigrade for about 20 hours followed by quenching in'water, and both heat treated and unheat treated test bars were subjected to that corrosion test which P T T prince comprises alternatelyimmersing the metal in,

and removingit from, a 3 per cent sodium chloride solution for about'80 h0urs,"a treatment referred to hereinafter as the alternate immersion treatment.

There are certain elements which may be added to the binary magnesium-lead alloys to particular advantage. Such, for instance,- are the .metals calcium, cadmium and zinc. These may be added singly or in combination with each other, the zinc in amounts between about 1.0 per cent and 10.0 percent, the calcium between about -0.1 per cent and 2.0" per cent, and the cadmium between about 1.0 per cent and 10.0.per cent.

These alloying elements are. substantial equiva-:

lents as indicated by their susceptibility to' thermal treatment in magnesium l'ead alloys- The calcium fayorably affects 'the casting properties of the alloy without markedlydecreasing its, corrosion resistanceH'Forinstance, a magnesium alloy containing 21.4 per "cent of leadand 0.25 per cent'of calcium shows, in the as cast con-' dition,' a strength loss of only 17 per cent afteralternate' immersion in a 3 percent sodium chloridesolution for about v80 hourspwhile a heat' treated magnesium alloy containing about 5 per cent of lead towhich about 0.25 per cent] of calcium had been added did not undergo any cadmium had in thesand cast condition a tensile strength of about 24,650 pounds per square inch and an elongation of about 9.8 per cent in 2 inches. After a heat treatment of about 20 hours at about 450 centigrade its tensile strength had increased to about 25,140 pounds per square inch and its elongation to 10.3 per cent in 2 inches.

' of lead; and about 5.0 per cent of cadmium. An

alloy of magnesium with about 5.0 per cent of lead and 5.0 per cent of zinc had in the sand cast condition a tensile strength of about 23,370 pounds per square inch. After. a thermal treatment of about 20 hours at 450 centigrade followed by an aging treatment of about 20 hours at 150 centigrade its strength had increased to about 25,710 pounds per square inch. After an alternate immersion corrosion test of 80 hours the loss in strength was only 12 per cent. Another alloy of magnesium with about 5.2 per cent of lead and 3.2 per cent of zinc under similar conditions lost only about 10 per cent after 80 hours alternate immersion inthe corrosive solution. As a preferred composition for alloys of this nature I advise 1) 5.0 per cent lead, 10 per cent calcium, balance magnesium; (2) 5.0 per cent lead, 5.0 per cent cadmium, balance magnesium; (3) 5.0 per cent lead, 5.0 per cent zinc, balance magnesium. If more than one of the elements calcium, cadmium, or zinc be present simultaneously, I prefer not to exceed a total of nesium-lead alloys and are substantially equivalent in this respect that they materially refine the grain structure of the'alloy. Aluminum, for instance, can be added over a wide range, such as between 1.0 and 15.0 per cent; silicon may be eflectively present forthis purpose in amounts of about 0.1 to 2.0 per cent. ,When used in combination it is advisable that the total content 'of aluminum and silicon does not exceed 15.0 per cent. In the preferred practice of my invention I have found that the best results are usually obtained when the aluminum is present in amounts U between 5 and 10 per cent.

As a preferred magnesium-lead-silicon composition I use a magnesiumbase alloy containing 7.0 per cent of lead and 0.5 per cent of silicon. As a preferred magnesium-lead-aluminum alloy- I use a magnesium-base alloy containing 7.0 per cent of lead and 5.0 per cent of aluminum. When the aluminum-and silicon are used in conjunction I Prefer to use a total of about 5.0 per cent of aluminum and silicon combined-for instance about 4.0 per cent aluminum and 1.0 per cent silicon;

Manganese alone may be added to magnesiumlead alloysin *amountsbetween 0.1 per cent and 1.0 percent and has a stabilizing effect upon the alloy properties in that it raises the hardness slightly, does not materially decrease the dormsion resistance, and adds to the matrix of the alioy a hardening element which expresses itself not only in an increase in tensile strength but also surface hardness. An alloy of this nature containing about 8.0 per cent of lead and 0.85 per cent of manganese lost only 6 per cent of its original strength after 80 hours alternate immersion in a 3 per cent aqueous solution of sodium chloride and in the solution heat treated condition lost only 7 per cent of its strength in the alternate immersion treatment. A magnesium alloy containing about 10.37 per cent of lead had lost only about 10 per cent of its strength at the expiration of this period as compared with certain other commercial alloys, such as, for instance, the well known magnesium alloy containing about 7 per .cent of aluminum and 0.4 per cent of manganese which, at the end of 40 hours of alternate immersion, had lost about per cent of its strength.

Very favorable alloys can be compounded by using as a base an alloy of magnesium, lead and aluminum and making additions thereto of at least one of the class of metals tin, manganese or zinc. The lead can be used in amounts from about 0.5 per cent to about 22.0 per cent, the aluminum from about 1.0 per cent to about 15.0 per cent, the tin from about 1.0 per cent to about 15.0

. per cent, the manganese from about 0.1 per cent to about 1.0 per cent, and the zinc from about 1.0 per cent to about 10.0 per cent. A sand cast alloy within this range had, in the as cast condition, a tensile strength of 27,500 pounds per square inch and an elongation of 5.7 per cent in 2 inches. After a thermal treatment of 16 hours at 315 centigrade, the alloy had a tensile strength of 29,640 pounds per square inch and an elongation of 6.0 per cent in 2 inches. Some of theheat treated specimens were then given an alternate immersion treatment for 40 hours and after the treatment the specimens had a tensile strength of 28,413 pounds per square inch and an elongation of5l8 per cent in 2 inches, this alloy containing 5.0 per cent of aluminum, 5.0 per cent of lead, 0.4 per cent of manganese and 2.0 per cent of zinc. The loss in strength on the corrosion treatment is observed to be less than 5 per cent as compared to about 60 'per cent with the commercial magnesium-aluminum-manganese alloy disclosed hereinbefore which contains about 7 per cent of aluminum and 0.4 per cent of manganese.

As preferred compositions for alloys of this nature a I advise (1) 7.0 percent of lead, 7.0 per cent of aluminum, 2.0 per cent tin, balance magnesium; (2) 7.0 percent-lead, 7.0 per cent aluminum. 2.0 per cent tin, 0.5 per cent manganese, balance magnesium; ,(3) 7.0 per cent lead, 7.0 per cent aluminum, 2.0 per cent tin, 2.0 per cent zinc, balance magnesium.

Two alloy compositions within this range which I have used to advantage are as follows: A mag-v with the addition of about 7 per cent of lead to an alloy containing 7 per cent of aluminum and 1 per cent of manganese, the loss of strength after 4/ the alternate immersion test was only about 30 per cent, as compared with about 60 per cent of the same alloy without lead.

Alloys of magnesium with lead, aluminum, and

manganese have been disclosed hereinabove. I havediscovered that if to a base alloy of magnesium-lead-aluminum-manganese I add one or more of the class of metals calcium or cadmium, the resulting alloys become considerably more susceptible to variation of properties by thermal treatments and their hardness can be markedly increased by artificial aging after thermal solution treatments. In these alloys the lead content should range from about 0.5 per cent to about 22.0 per cent, the aluminum from about 1.0 per cent to about 15.0 'per cent, and the manganese from about 0.1 per cent to about 1.0 per cent. To these elements as a common base I add the elements cal-, cium, or cadmium, singly or in combination, the calcium in amounts from about 0.1 per cent to about 2.0 per cent, the cadmium from about 1.0 per cent to about 10.0 per cent. As an example of an alloy of this nature, a sand cast specimen of a magnesium-base alloy containing about 10.0

and this hardness was raised toabout 84 by an additional aging treatmentof 20 hours at about 175 centigrade, the tensile strength increasing slightly to about 37,000 pounds per square inch; Similarly a. magnesium-base alloy containing about 5.0 per cent of lead, 7.0 percent of alumi-, num, 10.0 per cent of cadmium, and 0.4 per cent of manganese had in the sand cast condition a tensile strength of about 24,000 pounds per square inch. Aftera thermal treatment of 21 hours at about 430 centigrade the alloy had 'a tensile/ strength of about 35,000 pounds per square inch. An additional aging treatment raised the Brinell hardness of the-alloy from about 61 to about 79.

Similarly, a magnesium-base alloy containing about 5.0 per cent of lead, 10.0 per cent of cadmium, 7.0 per cent of aluminum, 1.0 per cent of;

manganese, and 0.25 percent of calcium had in the sand cast condition a tensile strength of about 24,290 pounds per square inch. Aftera thermal treatment of 20 hours at about 430 centigrade this alloy had a tensile strength of about 33,200 pounds per square inch. After an additional thermal treatment of about 20 hours at'about 150 centigrade the strength increased to about 35,600 pounds per square inch and the Brinell hardness from about 47 to about 66.

Another magnesium-base alloy" containing,-

about 10.0 per cent of lead, 7.0 per cent of aluminum, 5.0 per cent ofcadmium, 0.4 per cent of manganese, and 0.1 per cent of calcium, had in the sand cast condition a tensile strength of about 23,210 pounds per square inch. 'After a thermal solution treatment of 21 hours at about 430 centigrade the alloy had a tensile strength of about 36,030 pounds per square inch; the Brinell hardness was about 61. After an additional aging treatment of about 20 hours at about 175 centigrade its tensile strength was about 37,010 pounds per square inch and its Brinell hardness about 84. As. a desirable alloy of this nature I advise 7.0 per cent lead, 7.0 per cent aluminum and, 0.4 per cent manganese. If more the yield point of these alloys.

15.0 per cent.

- of the aluminum.

than one of the elements calcium or cadmium are present simultaneously, the total should not exceed about 10.0 per cent for preferred purposes. The addition of zinc in amounts from about 1.0 per cent to about 10.0 per cent to magnesium- 5 lead alloys containing aluminum and silicon in combination decreases the linear shrinkage, thus favorably afi'ecting the casting. properties, and also increases the corrosion resistance and raises In alloys of this type the lead should rangefrom 0.5 per cent to g 22.0 per cent, the aluminum from 1.0 per cent to 15.0 percent, and the 'silicon from 0.1 per cent to 2.0 per cent, but the total amount of aluminum and silicon should preferably not exceed A useful alloy of this nature is a magnesiumbase alloy containingabout 10.0 per cent lead, 8.0 percent aluminum "and 3.25 per cent zinc. Another useful composition is attained by substi- 20 tuting about 1.0 per cent silicon for part" or all An alloy'similarly improved in casting propv erties, although not to such a decided extent, is onecontaining, from about 0.5 per cent to 22.0 25

per cent of lead, from about 1.0 percent to about 10.0 per cent of zinc, and from about 0.1 per cent. "to about 2.0 per cent of silicon. A favorable alloy within this range is a magnesium-base alloy consisting of about 10.0 per cent of lead, about 3.25 per cent of zinc, and about 1.0 per cent of oxidizable metals.v The alloys, especially the .40

magnesium-lead binary alloys, may be extruded over the entire disclosed composition range, but other types of mechanical deformation such as rolling or forging should be carried'on with due regard for the fact that as the percentage of total added alloying elements increases, the necessity for precaution/in working the alloy also increases. v

It-is my object to retain, as far as possible, the advantages of the use of magnesium base, such 50 as .low specific gravity, while securing in addition the hereinabove disclosed benefits accruing from the additions of the other alloying elements herein outlined. Accordingly, where in the appended claims the term magnesium-base alloy is used, it refers to-an alloy containing more than approximately 50 per cent of'magnesium.

This application is a division of my copending application Serial No. 692,135, filed October 4, 1933. I claim: g 1. A magnesium-base alloy containing from about 0.5 to 22.0 per cent of lead,from about 1.0 to 15.0 per cent of aluminum, and from about 1.0 to 10.0 per cent of zinc, the balance being magnesium.

nor E. Pr me.