US2376868A - Magnesium alloy - Google Patents

Description

Patented May 29, 1945-,

MAGNESIUM ALLOY Reginald S. Dean and Clarence T. Anderson,

Salt Lake City, Utah, assignors to Chicago Development Company, Chicago, Ill., a corporation of Illinois No Drav'ving.- Original application october l,

1941, Serial No.

413,159, now Patent No.

2,317,980, May 4, 1943. Divided and this application May 20, 1942, Serial No. 443,824

4 Claims. (Cl. 75-168) Our invention relates to the preparation of magnesium-base alloys which are suitable for rolling into sheets and drawing into tubes and may also be extruded and treated, in general, in the usual manner in which magnesium or magnesium-base alloys are fabricated.

It is well known that a pure or substantially pure magnesium has a greater resistance to corroslon than magnesium-base alloys and that, of the *alloying elements which are conventionally added to magnesium, manganese. brings about the least .reduction of corrosion resistance. Heretofore, it has been exceedingly dimcult to add manganese to magnesium in amounts greater than about 1% to 2% manganese without obtaining a. non-homogeneous alloy.

As disclosed in'our copending application, Se-. rial No. 413,159, filed October 1, 1941,. whichissued on'May 4, 1943, as Patent No. 2,317,980,

and of which the present application is a division, I

wehave found that manganese may be'incorporated into magnesium in substantial amounts, in

r a relatively simple manner, without interfering with the desired homogeneity of the resultin alloy. Wehave therein disclosed that if lithium is added to magnesium, the amount of manganese which ordinarily can be incorporated with the magnesium without effecting production of" a non-homogeneous alloy may be substantially increased. The amount of manganese which may be incorporated with the magnesium to produce a homogeneous alloy is determined, in part, by the amount of lithium which is present. Thus, for example, with 5% lithium, of

maganese may be readily incorporated into magnesium with the production of a homogeneous alloy.

We have also found, as disclosed in our aforementioned copending application, that the addition of silver to the lithium-manganese-mag -v nesium alloys, described hereinabove, increases their strength in the cold rolled.,'condition and somewhat improves their casting properties. The amount of silver which brings about these properties is of a small order, from about 0.5% .to about 2.0% being sufllcient in at least most cases. a v

Our present application isdirected to those alloys containing from about 1% to about 10% lithium, from about 2% to about 10% manganese, a small amount'of silver, preferably from about 0.5% to about 2.0%, the balance being substantially all magnesium.

The following example is illustrative of alloys It will be understood that various changes may be made with respect to proportions of the alloying ingredients, within the'ranges set out hereinabove, and that other changes may be made without departing fromthe spirit of the inven tion in the light of the guiding principles which are disclosed herein.

Example An alloy was made containing 83% magnesium, 10% manganese, 5% lithium, and 2% silver, using redistilled magnesium, electrolytic manganese having a purity in excess of 99.9%..

and highly pure .grades of lithium and silver. The alloy was melted in a helium atmosphere. However, fluxes such as are used'for the commercial melting of magnesium-base alloys may be .used. to protect the surface of the metal during melting. The alloy, when cast, had a hardness of 40 when measured on the Rockwell F scale. The alloy may be cold rolled by any of the usual processes. When substantially fully cold worked, it had a hardness of 75 when measured on the Rockwell F scale. The density of the alloy was approximately 2.0. harder and stronger than at least most other magnesium-base alloys which have heretofore been madev available. 1 This "increased hardness and strength make the alloy particularly valuable for the construction of various parts of airplanes.

As we have indicated hereinabove, in the prac= tice of our invention we preferto employ alloying metalsof high purity. The magnesium, as we have indicated, is preferably a redistilled product.v The manganese, for best results, should be at least 99.0% pure and preferably of even greater purity. The manganese utilized may be produced by a vacuum distillation process but we prefer, particularly, toemploy electrolytic man-'- ganese having a purity of 'at least about 99.0%

and preferably of 99.9%.- The lithium, and silver where used, are also preferably of a high degree of purity.

What we claim as new and desire to protect by Letters Patent of the United States is:

1 Magnesium-base alloysv containing from about 1% to about 10% lithium, from about 2% to about 10% manganese, from about 0.5% to 2% silver, balance substantially-all magnesium.

2. Cold workedmagnesium-base alloys containing from about 1% to about 10% lithiumf from about 2% to about 10% electrolytic manga'nese having a purity of at least 99.9%, from made in accordance with our-present invention.

about 0.5% to. about 2.0% silver, balance sub- The alloy is considerably I stantially all magnesiuin, said alloys having a taining about 5% lithium, about 10% electrolytic 1 hardness in excess of 50 measured on the Rockmanganese having a purity of at least 99.9%,

wellFscale. from about 0.5% to about 2.0% silver, balance v 3. Magnesium-base alloys containing about 5% substantially all magnesium, said alloys havinglithium, about 10% manganese, from about 0.5% 5 a hardness in excess of 50 measured on the Rockj to 2.0% silver, balance substantially all magnewellFscale.

;- sium. REGINALD S. DEAN,

4,0o1d worked magnesium-base alloys con- 7 CLARENCE 'r,