US2095975A

US2095975A - Magnesium alloys

Info

Publication number: US2095975A
Application number: US35126A
Authority: US
Inventors: Edward F Fischer
Original assignee: MAGNESIUM DEV CORP
Current assignee: MAGNESIUM DEV CORP; MAGNESIUM DEVELOPMENT Corp
Priority date: 1935-08-07
Filing date: 1935-08-07
Publication date: 1937-10-19
Anticipated expiration: 1954-10-19

Description

Patented Oct. 19, 1937 UNITED STATES PATENT OFFICE mesne assignments, ment Corporation, a

to Magnesium Developcorporation of Delaware No Drawing. Application August I, 1935, Serial No. 35,126

3 Claims.

This invention relates to wrought magnesium base alloys and it is particularly concerned with those alloys which contain from about 5 to 10 per cent aluminum, 0.1 to 1 per cent manganese, 0.05 to 0.05 per cent calcium, and 0.1 to 1.5 per cent zinc.

Magnesium base alloys containing aluminum and zinc have proved to be quite satisfactory for the production of castings. Manganese is frequently added to these alloys for the purpose of improving their corrosion resistance, but it does not affect their casting quality to any substantial degree. Where attempts have been made to hot work these same alloys in the production of workability is obtained by limiting the aluminum content to less than about 3 per cent. However,

alloys containing 5 per cent or more aluminum have a higher strength and consequently are desired for many applications. Also,'as the aluminum content of these alloys is increased, they become more difllcult to work, especially at elevated temperatures; because of the tendency of the billets to crack when pressed, rolled, or forged. In order to successfully fabricate the alloys containing more than 5 per cent aluminum it has been necessary to exercise rigid control over the heating and working conditions. In other words, the attainment of high strength in alloys of the foregoing type is achieved at the expense of ease in hot'working. 1

In the production of wrought articles, the major portion of the reduction or change in shape is accomplished at an elevated temperature where the metal is much more plastic than at ordinary temperatures. As a matter of practice the deformation of the metal is performed well above the temperature at which strains would be developed of the character found in the cold worked product. alloys hot working is usually' done above about 600 Fahrenheit. At this and higher temperatures the alloys are readily shaped without leaving deleterious residual strains. Although the alloy becomes sufliciently plastic at these temperatures to be easily deformed, it may lose its cohesive quality to such an extent that cracks or incipient fractures are created under pressure of the hammer, roll, or plunger, which prevent it from being utilized in the subsequent manufacture of wrought articles. Some alloys are more prone to exhibit this behavior than others. Magnesium base alloys containing from about 5 to 10 percent aluminum, 0.1 to 1 per cent manganese, 0.05 to 0.5 per cent calcium, and 0.1 to 1.5 per cent zinc In the fabrication of magnesium base belong to this group which in terms of the art are called hot short. Particular pains must therefore be taken to avoid the formation of cracks with a consequent increase in cost of production.

My invention is directed toward overcoming the disadvantages enumerated hereinabove with respect to the hot working of magnesium-aluminum-manganese-zinc-calcium alloys. In particular, it is an object of my invention to improve the ductility of these alloys at elevated temperatures without detracting from their strength or other desirable properties. I have discovered that magnesium-aluminum-manganeserzinc-calcium alloys can be rendered more ductile under the conditions imposed by working at high temperatures, such as have been referred to above, by the addition of a small amount of lead amounting to from 0.1 to l per cent of the total weight of the alloy. I have found, in addition, that this alloying constituent does not substantially change or aifect other desirable properties of the base alloy, but only effects a remarkable and bene ficial change in its working characteristics at elevated temperatures. Further, I have determined that the hot working properties of magnesium-aluminum manganese-zinc-calcium alloys can be similarly improved by incorporating in the alloy an amount of thallium and cadmium varying in amount from 0.1 to l per cent of the total weight of the alloy. My improved alloys containing the metals lead, thallium, and cadmium, individually or collectively in combination,

to indicate the relative capacity of different alloys having the greatest elongation under the impact being considered the most ductile and susceptible to hot working without exhibiting cracks. An exceptionally high correlation has been established between the results of this test and the actual behavior of alloys when rolled, extruded, pressed, or forged. The test has therefore come to be treated as a reliable guide in ascertaining the relative workability of different alloys at elevated temperatures.

The effect of lead, thallium, and cadmium is illustrated in alloys of the composition indicated below which were extruded and heated to a temperature of 550 Fahrenheit, 600 Fahrenheit, the practicable minimum hot working temperature, 650 Fahrenheit, and 700 Fahrenheit, and broken in tension under impact. The temperature to which the particular bars were heated and the elongation of the broken test pieces are also shown in the table below.

Composition Per cent elongation in 2" at Al Zn Mn Ca Pb 'I l Cd 550 F. 600 F. 650 F. 700 F.

Patent No. 2,095,975.

While magnesium base alloys composed of magnesium, from about 5 to 10 per cent aluminum, 0.1 to l per cent manganese, 0.05 to 0.5 per cent calcium, 0.1 to 1.5 per cent zinc, and 0.1 to l per cent of at least one of the group of elements lead, thallium, and cadmium, may be satisfactorily hot worked; I have found that those alloys which are composed of magnesium, from about 6 to 9 per cent aluminum, 0.2 to 0.6 ,per cent manganese, 0.05 to 0.25 per cent calcium, 0.1 to 1.3 per cent zinc, and 0.2 to 0.75 per cent of at least one of the metals lead, thallium, and cadmium are particularly desirable in making wrought articles.

The alloy may be produced in any suitable manner. .I prefer, however, to add the heavy low melting point metals to the melt in elemental fonn, stirring the liquid bath sufliciently to prevent segregation or settling of the added substance.

I claim:

1. A magnesium base alloy containing from 5m 10 per cent aluminum, 0.1 to l per cen u manganese, 0.1 to 1.5 per cent zinc, 0.05 to 0.5 per cent calcium, and 0.1 to l per cent lead, and characterized by improved ductility and freedom from hot-shortness under mechanical deformation at elevated temperatures.

2. A magnesium. base alloy composed of from 6 to 9 per cent aluminum, 0.2 to 0.6 per cent manganese, 0.1 to 1.3 per cent zinc, 0.05 to 0.25 per cent calcium, and 0.2 to 0.75 per cent lead, the balance being magnesium.

3. A magnesium base alloy composed of 6.5 per centaluminum, 0.5 per cent zinc, 0.3 per cent manganese, 0.1 per cent calcium, and 0.3 to 0.7 per cent lead, the balance being magnesium.

EDWARD F. FISCHER.

CERTIFICATE OF CORRECTION.

October 19, 1.957.

' (Seal) EDWARD F. FISCHER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows Page 1, first column, line 5, for "0.05" second occurrence, read 0.5; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of November, A. o. 1957 Henry Van Arsdale Acting Commissioner of Patents to hot working without exhibiting cracks. An exceptionally high correlation has been established between the results of this test and the actual behavior of alloys when rolled, extruded, pressed, or forged. The test has therefore come to be treated as a reliable guide in ascertaining the relative workability of different alloys at elevated temperatures.