US2279712A - Magnesium base alloy - Google Patents

Description

htented Apr. 14, 1942 MAGNESIUM BASE ALLOY John C. McDonald, Midland, Micln, assignor to The Dow Chemical Company, Midland, Micla, a corporation of Michigan No Drawing. Application December 23, 1940, Serial No. 371,382

3 Claims.

The invention relates to magnesium base alloys and more particularly concerns an alloy of this nature having high tensile and yield strengths associated with a degree of formability desirable for forming operations.

Magnesium base alloys are being widely used in the 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 havinggood iormability or ductility permitting relatively sharp bends to be made without the.

'article developing external cracks, usually have inferior characteristics as regards their tensile 4 and yield strengths.

magnesium containing the ordinary impurities found in the commercially pure metal, such as traces of nickel, copper, silicon, and iron. A particularly desirable composition having a preferred combination of properties is one containing 3 per cent of silver, 3 per cent of aluminum, 5 per cent of cadmium, 3 per cent of zinc, and 0.3 per cent oi manganese.

The following table lists some of the properties of rolled sheet metal made from my new polynary alloy and compares these properties with those of related alloys. The new alloy is shown to have improved yield strength and tensile strength. The table also shows that the per cent elongation which is to be regarded as a measure of the Iormability or ductility of the alloy is of the high order necessary to render the alloy suitable for forming operations.

Table Nominal composition in percent (remaindekmagnesium) Annealed Cold rolled Percent Yield Tensile Yield Tensile Ag Al Cd Mn Zn elongation strength in strength in strength in strength in in 2 inches lbs./sq. in. lba/sq. in. Ilia/sq. in. lbs/sq. in.

3 10 r 0.5 3 18 28,000 43,000 44,000 52,000 0 10 0. 5 3 i2 20, 000 40, 000 45, 000 51, 000 6 3 0. 5 3 i0 32, 000 47, 000 47, 000 52, 000 6 3 10 0.5 18 ,000 45,000 ,000 50,000 6 3 10 0. 5 3 13 31,000 ,000 40,000 55,000

It is, accordingly, the principal object of the invention to provide a magnesium base alloy which can be made into rolled sheet and the like possessing a sumcient degree of ductility or formability at ordinary temperatures 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 invention resides in the discovery that a magnesium base alloy containing from about 0.4 to 12 per cent of silver, 0.3 to 10 per cent of aluminum, 1 to 15 per cent of cadmium, 0.3 to 6 per cent of zinc, and from 0.01 to l per cent of manganese possesses the aforementioned properties. The term magnesium" used herein and in the appended claims is intended to include The properties set forth in the above table under the term "annealed" were obtained by first rolling the alloys at a temperature of 600 to 650 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 the annealed specimens which exhibited the maximum elongation. The properties set forth under the term cold rolled were obtained by subjecting specimens of the A comparison of the properties listed in the above table shows that when the new alloy contains relatively small amounts of cadmium, the alloy possesses an exceptionally high degree of formability coupled with high tensile and yield properties. It will be noted that the combined properties of the new alloy are superior in every instance to those of related alloys. In the higher percentage range of cadmium it will be noted that the iormability characteristics, while still satisfactory; tend to fall of! some while the tensile and yield properties .markedlyimprove. Thus, the particular composition selected will depend upon the use for which the'specific composition is intended. For example, in those instances where a high degree of formability is of prime importance a composition will be selected containing lower percentages of cadmium, while in those instances where high tensile and yield properties are of prime importance higher percentages of the alloying ingredient cadmium will be employed.

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

The new alloy may be compounded by any of the methods usually employed formelting' and alloying metals with magnesium, "suchas by adding the alloying ingredients singly or jointly to a bath of molten magnesium which'is preferably protected from oxidation by a suitable It should be mentioned that. the amount of manganese that may be present in a given composition is dependent upon the amount of aluminum present. For example, when about 0.5 per cent aluminum is present, it is diificult to obtain an alloy, containing more than 1.0 per cent of manganese In compositions containing more aluminum, such as from 8 to 10 per cent, it is diil'icult to obtain an alloy containing more than 0.5 per cent of manganese.

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

I claim:

1. Amagnesium ,base alloy containing from 0.4 to 12 per cent of silver, from 0.3 to 10 per cent of aluminum, from 1 to 15 per cent of cadmium, from 0.3 to 6 per cent of zinc, and from 0.01 to 1 per cent of manganese, the balance being magnesium. v

2. A magnesium base alloy containing 3 per cent of silver, 3 per cent of aluminum, 5 per cent of cadmium, 3 per cent ofzinc, and'0.3 per cent of manganese, the balance being magnesium.

3. A magnesium base" alloy containing from 0.4 to 12 per cent of silver, 0.3 to 10 per cent of aluminum, 1 to, 15 percent of cadmium, 0.3 to 6 per cent of zinc, and 0.01 to 1 per cent of manganese and characterized by improved tensile and yield strengths inthe cold rolled state as comparedto a similar alloy devoid of aluminum.

' JOHN c. MCDONALD.