US2221245A - Magnesium base alloy - Google Patents

Description

Patented Nov. 12, 1940 mem smm nssn ALLOY Joseph D. Hanawalt and John C. McDonald, Midland, Mich., assignors to The Dow Chemical Company, Midland, Micln, a. corporation of Michigan No Dr wing. Application November 13,1939,

Serial No. 304,122

4 Claims. The invention relates tomagnesium base alloys and more particularly concerns alloys of this nature having a high degee offormability, coupled with other improved physical properties,

r such as high tensileand yield strengths. 9 Magnesium alloys are beingwidely used in the structural arts where a light weight metal 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 sheetmetal articles requiring forming operations, such as bending, drawing, and the like, has not progressed as rapidly due to the fact that, in general, alloys of good formability, permitting relatively sharp bends to be made with out the article developing external cracks, usually have inferior characteristics as regards their tensile and yield strengths.

It is, accordingly, the principal object of the sile strength a'nd'greatly increased yield strength is found in those alloys containing from between about 0.1 to 0.3 per cent of calcium and from 2 to 6 per cent of copper. The alloys containing higher percentages of alloying ingredients, such A as between from 0.3 to 1 per cent of calcium and 5, from 6 to 10 per cent of copper, while still having good ductility, have exceptionally high yield and tensile properties, and thus are especially suitable for use in casting as well as forming 10 operations. f I

The following table, listing some of the properties of-rolled sheet metal made from our new ternary alloys and comparing these properties with those of related binary alloys, illustrates the improvement in yield strength, tensile strength, ductility or formability, as represented by the per cent increase in elongation, of our new alloy over that of the closely related binary alloys.

Table Nominal composition in percen Annealed Cold rolled (magnesium=remainder) Yield Tensile Percent Yield Tensile Percent 25 Ga Cu strength strength elongation strength strength elongtalon in lhsJsq. in. in lbs/sq. in. in 2 inches in lbs./sq. in. in lbs./sq. in. in 2 inches 3.1 23,000 31,000 2 ,000 34,000 2 0. 3 3. 2 22, 000 34, 000 13 35, 000 41, 000 2 6. 0 24, 000 34, 000 3 29, 000 36, 000 l 2 0. 3 6.0 22, 000 84, 000 10 35, 000 41, 000 4 10. 0 28, 000 31, 000 1 Carnot be cold :01 led.

invention to provide a magnesium base alloy which can be made into rolled sheet or the like, possessing a suflicient degree of ductility or formability at ordinary temperatures to be sharply bent, drawn, or otherwise shaped, while having high tensile and yield strengths.

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

Our invention resides in the discovery that a magnesium base alloy composed of from about 0.05 to 1.0 per Cent of calcium and from 0.5 to 12 per cent of copper, the balance being substantially all magnesium, is endowed with the aforementioned properties. While'the property of excellent formability or ductility coupled with high tensile strength andyield strength is manifest over the entire range of composition indicated, we have found that in general the preferred combination of properties, such as the most desirable ductility coupled with high ten.

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 800 F., and thereafter annealing them at various tempera- 40 tures through a temperature range of from 400. to 800 F. The properties selected for the table were those of 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 800 F. to additional rolling in the cold state to bring about a total reduction 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 strengths, while having at least a 1 per cent elongation in 2 inches.

By comparison of the properties listed in the above'table, it will be observed that the related binary alloys. Similarly, in the higher percentages of alloying ingredients, the properties of the new ternary alloys show improvement over those of the related binary alloys.

While the new alloy is-most-usefulin wrought form, such as sheets, due to its form'ability char-' acteristics, it may also be suitably used in making castings, forgings, extruded forms, and. the like.

The new alloy may be compounded in any of the ways known to the art, such as by adding the alloying ingredients to molten magnesium under suitable flux. 'I'he flux should be substantially free from,magnesium chloride if the calcium content of the alloy is to be above 0.3

per cent. In those 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, but in this case it is usually preferable to add the calcium last and without too much stirring to prevent the loss of calcium into the flux.

1. A 'magnsium base alloy containing from 0.05 to 1 per cent of calcium and from 0.5 to 12 per cent of copper, the balance being magv nesiumr 2. A magnesium base alloy containing from 0.5 to 1 per cent of calcium and from 1.0 to

-12per cent nesium; v

3. A magnesium base alloy containing from of copper, the balance being mag- 0.1 to 0.3 per cent, of calcium and from 2 to 6 per cent of copper, the balance being magnesium.

4. A magnesium base alloy containing from 0.3 to 0.8 per cent of calcium and from 6 to 10 .per cent of copper, the balance being magnesium. a a JOSEPH D. HANAWALT. JOHN C. McDONALD. Y