US2124572A - Magnesium base alloy - Google Patents

Description

Patented July 26, 1938 MAGNESIUM BASE ALLOY, Joseph D. Hanawalt and Charles E. Nelson, Mid-.

land,

Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation 'ol Michigan No Drawing. 'Original application May 29, 1937,

Serial No. 145,564. Divided and this application April 14, 938, Serial No. 202,007

2 Claims. (01.15 16 This invention relates to magnesium alloys and more particularly to alloys containing the metals cadmium, manganese, and lead.

The object of this invention is to produce magnesium alloys having improved mechanical properties. Another object is to produce magnesium alloys that are amenable to heat treatment.

Other objects and advantages will appear as the 1 description proceeds.

This invention is based on the discovery that such improved and highly desirable combinations of properties are tobe found in alloys that con-.

. tain from about 0.5 to 22.0 per cent of lead, from about 0.1 to 1.5 per cent of manganese, and from about 1 to 10 per cent of cadmium. We have likewise discovered that these quaternary magnesium-cadmium-manganese-lead alloys may be improved by the addition of zinc in amounts ranging from about 1 to- 10 per cent. For many purposes We normally prefer to use an alloy containing per cent or more of magnesiumand not more than 20 per cent of total added metal.

The ternary magnesium-cadmium-manganese alloys are well known and have been described in United StatesPatent No. 1,910,432 to John A.

Gann and James B. Reid, dated May 23,1932. 1

These alloys have good properties in the'wrought condition and, hence, are suitable for the production of parts by plastic deformation opera tions but they are less satisfactory for they production of castings because of their relatively low properties in the cast and heat treated conditions. We have discovered, however, that these latter properties may be improved very materially by the addition of lead as illustrated, for example, by the addition of various amounts of lead to a ternary alloy containing 2 per cent of cadmium and 1.5 per cent of manganese.

The presence of lead in the alloy likewise improves the yield strength but exerts very little effect on the percentage elongation and on the Brinell hardness.

Somewhat higher properties are obtained in ning'f larger percentages of cadmium.

5* per cent of manganese, and 2 to 6 per'cent-,of;ulead have tensile strengths of approximately 24,000 pounds per square inch, while in the heat treated and in the heat treated and aged conditions these same compositions show tensile strengths as high as 26,800 pounds per square inch.

We have likewise discovered that these new quaternary alloys of magnesium, cadmium, manganese, and lead may be still further improved by the addition of zinc. This improvement is particularly pronounced in the case of strength characteristics such as tensile strength, yield strength, and Brinell hardness. While the beneficial effect of zinc is very marked in the as cast alloys, the greatest benefits due to the presence of zinc are found in the heat treated and in the heat treated and aged alloys. Typical examples of such improvements are given in the follow- Cast alloys Tensile stren th lb./sq.in.

Yield stren th lb./sq.in.

Brinell hardness Heat treated and aged alloys The use for which the alloy is intended is an important factor in establishing its composition.

east alloys containing 8 per cent Alloys for fabrication by plastic deformation operations should, in general, contain about 2 to 5 er cent of cadmium, 0.5 to 1.5 per cent of manganese, 2 to 8 per cent of lead. and not more than 3 per cent of zinc. 0n the other hand, where high strength and hardness are required, we normally prefer a heat treated or heat treated and aged alloy containing about 2 to 8 per cent of cadmium, 0.5 to 1.5 per cent of manganese, 6 to 12 per cent of lead, and 2 to 6 per cent of zinc.

These new polynary alloys may be prepared by the well known methods of alloying metals with magnesium, such as by adding the respective alloying ingredients to a bath of molten metal protected from oxidation by a cover of a fluid flux. The metals may be added individually, simultaneously, or as hardeners prepared from two or more of said metals. Castings may be prepared by die casting or the like, or by sand casting in molding sand treated with an oxida tion inhibitor, such as sulfur or ammonium fluoride. Heat treatment may be carried out by heating the alloy for approximately 18 hours at 450 0. Aging may consist of a subsequent heating for 16 to 18 hours atapproximately 175 C.

Plastic deformation operations are best conducted in the temperature range of 300 to 400 C.

This application is a division of our copending application Serial No. 145,564, filed May 29, 1937.

Other modes of applying the principle of our invention may be employed instead of those explained, change being made as regards the ingredients herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

We particularly point out and distinctly claim JOSEPH D. HANAWALT. CHARLES E. NELSON;