US2233265A - Magnesium base alloy - Google Patents

Description

mg external cracks Patented Feb. 25, 1941 PATENT OFFICE MAGNE SIUM BASE ALLOY John C. McDonald, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich, I a corporation of Michigan- No Drawing. Application December 26, 1939, Serial No. 311,002

3 Claims.

The invention relates to magnesium base alloys and more particularly concerns an alloy of this nature having a high degree of formability associated with other desirable physical properties, such as good tensile and yield strengths.

Magnesium alloys are being widely used in various structural and mechanical 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, draw- ,ing, and the like, has not progressed as rapidly due to the fact that in general alloys having good iormability, permitting relatively sharp bends to be made without the article develop- V usually have "inferior strength characteristics.

It is, accordingly, the principal object of the invention to provide a magnesium base alloy which can be made into rolled sheet or the like, possessing sufflcient ductility or iormability to be sharply bent, drawn, or otherwise shaped while having good tensile and yield strengths.

Other objects and advantages will be apparent as the description of the invention proceeds. My inventionresides in the discovery that a magnesium base alloy composed 01' from 0.3 to

10 per cent of silver, 1 to 15 per cent cadmium,

0.3 to 10 per cent aluminum, and from 0.01 to 1 per ceint of calcium, the balance being. substantially all magnesium, is endowed with the store-mentioned properties. While the properties of good iormability or ductility associated with high tensile and yield strengths are manifest over the entire range of composition indicated, I have found that insgeneral the preferred combination of properties, such' as the most desirable ductility for forming operations, coupled with exceptionally high tensile strength and yield strength, is obtained when the alloy con-- tains from 0.5 to 5 per cent of silver, from 4 to 8 per cent oi cadmium, 0.1' to 0.3 per cent .of calcium, and from 1 to 5 per cent aluminum.

The specific proportion 01' each alloying metal and the total amount of the added alloying metals to be employed in the new alloy depends upon the use for which the alloyis intended. In general, itis preferable that the alloys contain more than about 715 per cent oi magnesium and less than 25 per cent of the added metals.

For example, in alloys where exceptionally good portance, the total added metals should not materially exceed 10 per cent; while in those instances where exceptionally high yield and tensile strengths are desirable, the total added metals may amount to as much as 15 per cent.

The following table lists some of the properties of rolled sheet metal made from my new quinary alloy and compares these properties with those of rolled sheet made from related quaternary alloys. A comparison of the propertiesillustrates the improvement of the strength characteristics 01' the new alloy over that of the closely related alloys. In the table the per cent elongation is to be regarded as a measure of the ductility or formability of the specimen.

. Table Nominal composition in percent (remsinder- Annealed magnesium) 1 Yield Tensile r) Percent Ag Al Cd Ca strengthin strengthin elongation lbs/sq. in. lbalsq. in. in2inches The properties listed in the above table under the section headed by the term annealed were obtained by first rolling the alloys at a temperature between about 600 to 700 F. and'thereafter annealing them at various temperatures in the temperature range from 400 to 800 F. properties selected for the. table were-those of the annealed specimens which exhibited the maximum elongation. a

By comparisonoi' the properties listed in the above table, it will be observed that the combined properties or my new polynary alloy are superior to those of the quaternary alloys having similar I percentages of alloying ingredients. For example, it will he noted that the composition containing lower percentages of alloying ingredients have improved elongation coupled with superior yield and tensile properties inthe annealed state; while those having higher percentages of alloy- .ing ingredients show superior strength characteristics as well as good elongation or formability; Similarly, improvements will be noted through- The out the range of alloying ingredients indicated.

While the new alloy is most useful in the wrought form, such as sheets, due to its formability characteristics, it may also be suitably used in making castings, forgings, extruded forms, and the like. It is further pointed out that my new alloy is amenable to solution and precipitation heat treatments, which, accordingly, modify its properties.

The new alloy may be compounded in any of the ways known in the art, such as by adding the ingredients to molten magnesium under suitable flux. The flux should be substantially free from magnesium chloride, if the calcium content is to be 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 without exerting undue deleterious efiects, but in this case it is usually preferable to add the calcium last without too much stirring or agitation in order that the loss of calcium in the flux will be substantially prevented.

I claim:

1. A magnesium base alloy containing from 0.3 to 10 per cent of silver, 1 to 15 per cent of cadmium, 0.3 to 10 per cent on aluminum, and

from0. 01 to:1 'per cent of calcium, the balance