US2221251A - Magnesium base alloy - Google Patents

Description

Patented Nov. 12, 1940 MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mich., assignor to The Dow Chemical Company, Midland, Micht, a corporation of Michigan Ne Drawing. Application November 13, 1939, Serial No. 304,128

3 Claims. (01. 75-168) The invention relates to magnesium base alloys, and more particularly concerns alloys of this nature having improved physical properties, such as a high degree of formability associated b with excellent tensile and yield strengths.

Magnesium alloys are finding increasing use in structural and mechanical arts where a light weightmetal is highly desirable, such as for use in making large castings, forgings, and the like.

However, the use of these alloys in the rolled form to make sheet metal articles requiring forming operations has not progressed as rapidly, due to the fact that in general alloys of good formability permitting relatively sharp bends to be made without the article developing external cracks usually have inferior characteristics as regards their yield and tensile strengths.

the alloy contains from 3 to 6 per cent of silver, from 0.1 to 0.3 per cent of calcium, and from 6 to 8 per cent of cadmium. Alloys containing higher percentages of alloying ingredients, while still having good ductility, have exceptionally 5 high yield and tensile strengths, and thus are also very suitable for use in casting operations as well as forming operations.

The following table, which lists some of the properties of rolled sheet metal made from my 10 new alloy and compares these properties with those of related parent alloys, illustrates the improvement in yield strength, tensile strength, and ductility as represented by the per cent increase in elongation of the new alloy over the corre- 5 sponding properties of the closely related ternary alloys.

Table Nominalcomposition in 20 percent (balanee Annealed 001d rolled magnesium Yield Tensile Per cent Yield Tensile Per cent Ag Ca Cd strength strength elongation strength strength elongation I inlbalsq. in. in lbs/sq. in in 2 inches in lbs/sq. in." in1bs./sq.in. in 2 inches 25 0. 3 5. 1 10, 000 31, 000 15 31, 000 30, 000 2 0. s 4.3 10,000 31,000 14 27,000 34,000 2 3'3 3'2 55% it 2 22m t 013 914 151000 321000 17 32,000 331000 2 30 It is, accordingly, the principal object of the invention to provide a magnesium base alloy which may be made into a rolled sheet or the like, possessing a sufficient degree of ductility or iormability to be sharply bent, drawn, or otherwise shaped, while still having excellent tensile and yield strengths. Other objects and advantages will be apparen as the description of the invention proceeds. My invention resides inthe discovery that a magnesium base alloy composed of from 0.5 to 10 per cent of silver, 0.05 to 1 per cent of calcium, and 1 to 15 per cent of cadium, the balance being substantially all magnesium, is endowed with the aforementioned properties. While the properties of improved formability, associated with high tensile and yield strengths, are manifest over the entire range of composition indicated,

I have found that in general a preferred com-- bination of properties, such as the most desirable ductility for forming operations together with high tensile and yield strengths, is obtained when The properties listed in the above table under the section headed by the term annealed were 35 obtained by first rolling the alloys at a temperature between about 600 to 800 F., and thereafter annealing them at various temperatures through a temperature range of from 400 to 800 F. The properties selected for the table were those of 40 the annealed specimens which exhibited the maximum elongation. The properties listed under the, section headed cold rolled were obtained by subjecting specimens of the alloys which had been hot rolled at a temperature of from 600 to 45 800 F. to additional rolling in the cold state to bring about a total reduction in thickness of from 2 to 10 per cent. The properties selected for the table were those of the cold rolled specimens which showed the greatest tensile and yield 50 strengths, while having at least a 1 per cent elongation in 2 inches. 3

By comparison of the properties listed in the above table, it will be observed that the'combined properties of my new quarternary alloy 55 will be noted in the other portions of the amenable to solution and precipitation heat treatments which, accordingly, modify its prop erties.

The new alloy may be compounded in any of the ways known in the art, such as by adding the alloying ingredients to the molten magnesium under a suitable flux. The flux should be free from magnesium chloride if the calcium content of the alloy is to be above 0.3 per cent. In those I For example, it will be noted.

instances where an alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be present in the flux without exerting a deleterious efiect, but in this case it is usually preferable to add the calcium last and without too much stirring in order that the loss of calcium into the flux will be substantially prevented.

I claim:

1. A magnesium base alloy containing from 0.5 to 10 per cent of silver, from 0.05 to 1 per cent of calcium, and from 11:0 15 per cent of cadmium, the balance being magnesium.

2. A magnesium base alloy containing from 2 to 8 per cent'of silver, from 0.1 to 0.5 per cent of calcium, and from 4 to 10 per cent of cadmium, the balance being magnesium.

3. A magnesium base alloy containing from 3 to 6 per cent of silver, from 0.1 to 0.3 per cent of calcium, and from 6 to 8 per cent of cadmium, 20

the balance being magnesium.

JOHN C. MCDONALD.