US2233954A - Magnesium base alloy - Google Patents

Description

Patented Mar. 4, 1941 PATENT OFFICE MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Application March 30, 1940,

Serial No. 327,034

30mins. (01. 75-103 This invention relates to magnesium base alloys and more particularly concerns an alloy of this nature having an excellent degree of formability associated with other desirable physical 5 properties such as high tensile and yield strengths.

Magnesium alloys are being widely used in the various structural and mechanical arts where a light weight metal is highly desirable, such as 10 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, drawing and the like, has not progressed as rapidly due to the 15 -fact that in general alloys of good formability permitting relatively sharp bends to be made without the articles developing external cracks usually have inferior strength characteristics.

It is accordingly the principal object of the in- 20 vention to provide a magnesium base alloy which can be made into rolled sheet or the like possess ing a suflicient degree of ductility or formability to be sharply bent, drawn, or otherwise shaped while having good tensile-and yield strengths.

is obtained when the alloy contains from 1 to 5 percent of zinc, from 2 to. 8 per cent of thallium, and from 0.05 to 0.4 per cent of calcium. The specific proportion of each alloying metal and the total amount of the alloyin metals to be 5 .added depends upon the use for which the alloy is intended. For example, where excellent ductility or formability associated with good yield and tensile strengths is of principal importance, the alloy should preferably contain from 0.5 to 10 1.5 per cent of zinc, 2 to '7 per cent of thallium, and from 0.05 to 0.4 per cent of calcium. However, in those instances where exceptionally high yield and tensile strengths .are more important than formability characteristics the alloy may contain increased amounts of thallium and zinc.

The following table lists some of the properties of rolled'sheet metal made from my new quaternary alloy and compares these properties with those of rolled sheet made from related ternar alloys. A comparison of the properties listed illustrates the improvement in the forma-' bility and strength characteristics of the new alloy over that of the closely'related ternary alloys.-

Other objects and advantages will be apparent In the table the per cent elongation is to be reas the description of theinvention proceeds. garded as a measure of the ductility or forma- My invention resides in the discovery that a bility of the specimen.

Table 30 zg ggggf t Annealed Cold rolled Yield .Tcnsile Percent Yield Tensile Zn T] Ca Strength strength elongation strength strength 35 mlbs./sq.1n. inlbs./sq.m. mZinches inlbsJsq. in. inlbsJsq. in.

a magnesium base alloy composed of from 0.3 to 8 The properties hsted 1n the above table under per cent of zinc, from 1 to 20 per cent of thallium, the section headed by the term annealed" were and from 0.01 to 1 per cent of calcium, the balobtained by first rolling the alloys at a temperaance being substantially all magnesium, 'is enture' of from 400 to 550 F. and thereafter an,-

dowed with .the afore-mentioned properties. nealing them at various temperatures, in the While the properties of excellent iormability or temperature range from 400 to 800 F. .The ductility associated with high tensile and yield properties selected for the table were those of the strengths are manifest over the entire range of annealed specimens which exhibited the maxithe composition indicated, I have found that in mum elongation. Properties listed in the above general the preferred combination of properties 55 table under the section "cold rolled" were obtained by subjecting specimens of the alloy which had been hot rolled at a temperature of from 400 to 550 F. to additional rolling in the cold 7 state in order'to improve their strength charac teristics. The properties selected for the table were of the cold rolled specimens which showed the greatest tensile and yield strengths while having at least 1 per cent elongation in 2 inches.

By comparison of the properties listed in the above table, it will be observed that the combined properties of my new quaternary alloy are superior to those of closely related ternary alloys having similar percentages of alloying ingredients. For .example, it will be noted that the alloys containing the lower percentages of alloying ingredients have an exceptionally high elongation or formability coupled with superior strength characteristics in both the annealed and cold rolled state. In the higher percentages of alloying ingredients the formability or ductility is fairly good, while the strength characteristics show an exceptionally high degree of improvement. Similar improvement will be noted I throughout the range of alloying ingredients in-- dicated.

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 v the ways known in the art, such as by adding the much stirring or agitation in order to guard against loss of some of the calcium into the flux.

I claim:

1. A magnesium base alloy containing from 0.3 to 8'per cent of zinc, from 1 to 20 per cent of thallium, and from 0.01 to 1 per cent of calcium, the balance being magnesium.

' 2. A magnesium base alloy containing from 0.5 to 1.5 per cent of zinc, from 3 to 7 per cent thallium, and from 0.05 to 0.4 per cent of calcium, the 25 balance being magnesium.

3. A magnesium base alloy containing from 4 to 6 per cent of zinc, from 3 to '7 per cent of thallium, and from 0.05 to 0.4 per cent of calcium, the balance being magnesium.

J C. MCDONALD.