US2507714A - Magnesium-base alloys - Google Patents

Description

Patented May 16, 1950 MAGNESIUM-BASE ALLOYS Alfred H. Hesse, Worthington, Ohio, assignor, by mesne assignments, to Mathieson Chemical Corporation, a corporation of Virginia No Drawing. Application September 14, 1945, Serial No. 616,160

This invention relates to magnesium-base alloys and has for its object the provision of an improved magnesium-base alloy comprising lithium and zinc, together with one or more of the metals silver, cadmium and aluminum. More particularly, the invention provides an alloy comprising magnesium as the principal constituent, from around 1% to 13% of lithium, from 1% to 10% of zinc, and with one or more of the metals silver, cadmium or aluminum. The silver and cadmium may be present in amounts from 1% to 10% and parts of these metals may be replaced with aluminum. Aluminum may also be used without silver or cadmium in amounts from 1 Claim. (Cl. 75-168) of about 1300 to 1400 F. may be used for alloying operations. After thorough agitation to insure homogeneity, the melt is allowed to settle at temperatures sufiicient to maintain it in a liquid state, after which it is decanted into molds. A suitable casting temperature is, for example, about 1320 F. The alloy may be cast directly into permanent molds without the necessity of providing a neutral or reducing atmosphere.

To insure the absence of harmful amounts of sodium or potassium, I prefer to prepare these alloys as described in my copending application, Serial No. 603,749, filed July 7, 1945. In accordance with that application, I prefer to use a flux g ffi g g f yig ggz gg g g ig ggg 3: 15 made up of one part of lithium fluoride to three rt tility, high tensile strength and good cold-workpa 5 nthmm cmmqe Use 9 flux I serves to reduce the sodium and potassium conmg properties. Certain of these alloys have extent of the alloy I may also treat the alloy b celent creep resistance and stability of tensile blowing the melt with a as such as mtr y properties at room temperature. Some of them 29 t n q are susceptible to heat treatment. 01 i i o accomp S decrease in sodmm or po ass um.

The new alloys of the 1nvent1on may be prepared by any of the usual melting processes with In the i the hthmm precautions to prevent an excessive sodium confluonde thlfkened ajfter tamination. For example, the magnesium may 35 1101131111 addltlon by surfing mgh meltmg" be melted in an iron crucible under a suitable pomt oxide or compound into the These flux, and then zinc, silver, cadmium, or l materials, by thickening the flux, tend to cause 1mm, is added, as required, followed by the addia better fiuximetal separation Oxides found tion of lithium. In order to avoid excessive oxida- Suitable for thls p p e aremolybdenum sesquition of the lithium during the alloying process, it 0 Oxlde- Y acid, nla-gneslum 0x159, and boric is advisable to use means for holding the lightanhydllde- T1165? Oxides (10 not ppea to enweight lithium beneath the surface of the molten hence the propertles f e a oy ut do provide metal. An inverted perforated steel cup, such as cleaner metals at lower melting losses. Illustraa phosphorizing cup or an analogous device suittive examples of alloys of this invention are given able for this purpose, may be used. Temperatures 35 in the following table:

Percentages Per cent N0 552;??? Reduc- Yield Tensile on tion 1n Strength Strength Mg Li Zn Ag Cd Al Area The above alloys had specific gravitles varying irom around 1.05 to 1.57.

The tensile properties were measured on rod, extruded from the castings.

Alloys Nos. 5 and 6 of the table show remarkable stability of physical properties at room temperature. Their creep properties are comparable to the best commercially available aluminumbase alloys.

Both of these alloys are susceptible to heat treatment. For example, the extruded hardness of No. 5, about 93 Rockwell E, is lowered to 88 when quenched from 500 F. Following the. quench, the hardness may then be increased to about 98 Rockwell E after a 200 F. aging;treat;- ment. Alloy No. 6 shows a hardness on extrusion of about 90 Rockwell E. This is lowered to 7'7 by heating to from 500 to 700 F. and. quenching. A sixteen hour heat treatment at 150 F. restores the hardness to approximately 96 Rockwell E. Thus, these alloys should lend themselves readily to cold-forming in the soft or quenched condition, and when formed may be converted to a strong structural material by the low-temperature heat treatment.

In. describing and in claiming the various percentages of metals used in the alloys, it is understood that they include the ordinary impurities found in the commercial metals. lithium, as ordinarily produced, contains objectionable amounts of sodium, the sodium may be substantially eliminated by the methods of refining herein described.

While I claim:

A magnesium-base alloy comprising from 1% to 13% of lithium, from 1% to 10% of zinc, from 1% to 10% of at least one metal of the group consisting of silver and cadmium, from 0.5% to 6% of aluminum and the balance magnesium.

ALFRED H. HESSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,226,550 Burkhardt Dec. 31, 1940 2,261,905 Nelson et a1 Nov. 4, 1941 2,305,825 Burkhardt Dec. 22, 1942 2,317,980 Dean May 4, 1943 2,385,685 Busk Sept. 25, 1945 FOREIGN PATENTS Number Country Date 524,511 Great Britain July 30, 1940 361,086 Germany Oct. 10, 1922 509,024 Germany Oct. 6, 1930- OTHER. REFERENCES A. P. 6. application of Burkhardt, Serial No. 303,611, pub. May 4, 1943.

Henry et al., Lithium-Magnesium Equilibrium Diagram, Trans. Amer. Inst. Mining and Metallurgical Engrs, 1934, vol. III, pp. 319-332.