US2270192A - Magnesium base alloy - Google Patents

Description

Patented Jan. 13, 1942 moan-sum BASE ALLOY John McDonald, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich a corporation of Michigan No Drawing.

inthe structural. arts where a light weight metal is highly desirable, such as'for use in making castings, forgings, and'the like. However, the use of these alloys in the rolled form to .make sheet metal articles requiring forming operations, such as bending and drawing, has not progressed as rapidly due to the fact that, in general, alloys having good formability or ductility permitting relatively sharp bends to be made without the article developing external cracks usually have inferior characteristics as regards their tensile and yield strengths. 1

It is, accordingly, the principal object of the invention to provide a magnesium base alloy which can be made into rolled sheets and the like possessing a suflicient degree of ductility or formability at ordinary temperatures to be Application December 23, 1940, Serial No. 371,374

strengths coupled with satisfactory formability are manifest over the entire range of composi tion indicated, I have found that in general an alloy containing from about 0.05 to 0.5 per cent of calcium, 1.5 to 2.5 per cent of manganese, and from 3 to 8 per cent of thallium, possesses the most satisfactory combination of properties. A particularly desirable composition is one containing 0.15 per cent of calcium, 2 per cent of manganese, and 5 per cent of thallium.

The following tablelisting some of the properties of rolled sheet metal made from my new quaternary alloy and comparing these properties with those of related ternary alloys, illustrates the improvement in strength characteristics of my new alloy. over that of related commercial alloys and at the same time shows that the per Table Nominal composition percen Annealed Cold rolled (remaindermagnesium) Percent Yield Tensile Yield Tensile Ca Mn Tl elon tion strengthin strengthin strengthin strength in infl chee lbsJsq. in. lbs./sq. in. lbs/sq. in. lbs./sq. in.

sharply bent, drawn, or otherwise shaped, while having highly improved tensile and yield strengths.

Other objects and advantages will be apparent as the description of this invention proceeds.

My invention resides in the discovery that a magnesium base alloy containing from 0.01 to 1 per cent of calcium, 0.01 to 3 per cent of manganese, and from 1 to 12.per cent of, thallium possesses the aforementioned desirable properties. The term magnesium used herein and in the appended claims is intended to include magnesium containing the ordinaryimpurities found in the commercially pure metal, such as traces of copper, silicon, nickel, and iron.

While the properties of high tensile and yield The properties set forth above under the term annealed were obtained by first rolling specimens of the alloys at a temperature of 550 F.

and thereafter annealing them at various tem- A comparison of the properties listed in the table shows that the yield and tensile strengths in both the annealed and cold rolled state is markedly superior to those of related alloys, while it will be noted that the per cent elongati on is only slightly inferior to that of the related alloys showing the highest degree of formability.

The new alloy may be compounded by any of the methods usually employed for melting and alloying metal with magnesium, such as by adding the alloying ingredients singly or jointly to a bath of molten magnesium which is preferably protected from oxidation by a suitable flux. The

flux should be substantially free from magnesium chloride if the calcium content of the alloy is above 0.3 per cent. In those instances where the alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be present in the flux, but in this case it is preferable to add the calcium last and without too much stirring and agitation to prevent loss of calcium into the flux.

It is to be understood that the invention is not limited to the specific composition herein described but may take other forms without departing from the scope of the invention.

I claim: A

1. A magnesium base alloy containing from about 0.01 to l per cent of calcium, from about 0.01 to 3 per cent of manganese, and from 1 to 12 per cent of thallium, the balance being magneslum.

2. A magnesium base alloy containing from about 0.05 to 0.5 per cent of calcium, from 0.5 to 2.5 per cent of manganese, from 3 to 8 per cent of thallium, the balance being magnesium.

3. A magnesium base alloy containing 0.15 per cent of calcium, 2 per cent of manganese, 5 per cent of thallium, the balance being magnesium.

4. A magnesium base alloy containing from 0.01 to 1 per cent of calcium, about 0.01 to 3 per cent of manganese, and about 1 to 12 per cent of thallium and characterized by improved tensile strength and yield strength as compared to a similar magnesium-calcium-manganese alloy devoid of thallium.

JOHN C. McDONALD.