US2124571A - Magnesium base alloy - Google Patents

Description

Patented July 26, 1938 MAGNESIUMB ASE'ALl DY Joseph D. Hanawalt and Charles E. Nelson, Midland, Mich., assignors to The Dow Chemical Company, Midland, Michigan- Micln, a corporation of 7 N0 Drawing. Application May 20, lasasensi I j 2 Claims. (Cl. -168) This invention relates to magnesium alloys and more particularly to alloys containing the metals cadmium, manganese, and'lead;

The bject 01' 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 description proceeds. v

This invention is based on the discovery that such improved and highly desirable combinations 01 properties are to be found in alloys that contain 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 01' cadmium. We have like wisediscoveredthatthese quaternary magnesiumcadmium-manganese-lead alloys may be improved by the addition of zinc in amounts ranging ironi about 1 to 10 per cent. For many pur- 0 poses we normally prefer to use an alloy containing per cent or more 01' magnesium and 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 States Patent No. 1,910,432 to John A. Gann and James B. Reid dated May 23, 1932. These alloys have good properties in the wrought condition and, hence, are suitable for the production 01' parts by plastic deformation operations but they are less satisfactory for the 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 01' lead as illustrated, for example, by the addition of various amounts oi 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 alloys containing larger percentages oi. cadmium.

" For example, cast alloys containing 8 per cent of cadmium, 1.5 per, cent oi manganese, and: 2 to 6 per cent oi? leadhavetensile strengths, ctap- I proximately 24,000 pounds per square inch, while "in' the heat treated and in the heat treated and "aged conditions these same composition's'show tensile strengths as high as 26,800 pounds'per square inch. i

We have likewise discovered that these new quaternary alloys of magnesium, cadmium, man ganese, and lead may be still further improved by the addition oi! zinc. This improvement is particularly pronounced in the case of strength characteristics such as tensile strength, yield strength,

and Brinell hardness. While the beneficial eflect of zinc is very marked in the as cast alloys, the greatest benefits due towthe presence of zinc are found in the heat treated and in the heat treated and aged alloys. Typical examples 01' such improvements are given in the following tables:

Cast allows Tensile Yield Composition at n h, stre l1, Brine lbf/ sqfin. 10.102910. W

Mg-wg, o0+1.0% MM- 127 b 20,400 0, m fia 0d+l.6% Mn+ m 12% b+3% Zn 20, 0 0,000 41.1 t i s" Cd+1'6% Mn+ 24,010 000 M f-%;6& i3%'fifi 27 m 2 0 g n 38-6 Mg+87 c 1+1w Mn+ 0% P1+0% Zn. 25,000 I 10, 000 40 2 Heat treated alloys M +2z, Cd+1.5% Mn+ 127 b 000 Mg+ 2% Od+l.5% 0111+ Mm 12% b+5%Zn 00,10 10,000 400 a MM 24000 0,400 ass Mg l-sV "6d i i. fin

0% Pfi+0% 20.11--.-1 30,400 11,000 47.0

Heat treated and aged alloys Mg+ Cd+l.07 M11+ 1295 -1. 20200 0,000 00.2 s+ 0 Cd+l.5% Mn+ 12% b+i5% Zn 37,100 20,400 000 Mg+8% c0+1.0% Mn+ 0 ,rs r 20,000 0,400 sac Mg+8% c0+1.0% Mn+ I 31,000 11, 000 00. o

l1 0% Pi+c% 211-1 41, 000 21,100 700 The use for which the alloy is intended is an important factor in establishing its composition. Alloys for fabrication by plastic deformation operations should, in general, contain about 2 to per cent of cadmium, 0.5 to 1.5 per cent 1 of manganese,2to B'per cent of lead, and not more 'than 3 .per' cent 01 zinc.

protected from oxidation by a' cover of a fluid' flux. The metals may be added, individually, simultaneously, or 'as hardeners prepared from two or moreotsaid metals. Castings may be prepared by die casting or the like, vor bysand ,castin'g in molding", sand treated with an oxidation I inhibitor, such as sulfur 'or ammonium fluoride. I Heat treatment maybe carried out by heating the alloy for approximately 18 hours at 450 C.

Aging may consist of a subsequent heating for Y 16 to 18 hours at approximately 175 C. Plastic deformation operations are best conducted in the temperature range of 300 to 400 C.

Other modes of applyingthe 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.

I y We particularly point out and distinctly claim asour invention:

1. A magnesium-base alloy containing from about 1 to percent of cadmium, from about 0.1 to 1.5 per cent of manganese, from about 0.5 to 22 per cent of lead, the balance being mag,-

nesium. e

.2; A magnesium-base alloy containing from about 2 to 5 per cent of cadmium, from about 0.5v to 1.5 per cent of manganese, from about to 8 per cent of lead, the balance being' rnagnesiuln.

f JOSEPH D; HANAWALT. CHARLES E. NELSON,-