US2178574A - Magnesium base alloy - Google Patents

Description

per, from about Patented Nov.- 1939 John A. Gann,

Dow Chemical Company,

poration of Michigan No Drawing.

The present invention relates to magnesium alloys and particularly to those in which magnesium predominates.

Binary alloys of magnesium and copper have been known for a long time, but they have not been used commercially because of their relatively low mechanical properties and their poor corrosion resistance.

The primary object of this invention is to produce magnesium alloys containing copper, having improved mechanical properties and corrosion resistance; Another object is to produce magnesium alloys containing copper that are amenable to heat treatment. Other objects and advantages will appear as The invention is based on the discovery that the properties and characteristics of the binary magnesium-copper alloys can be enhanced very materially by the addition of definite amounts of lead and that these ternary magnesium-copperlead alloys can be further improved by the addition of definite amounts of at least one of the low melting metals tin and zinc.

I have discovered thatbeneflcial effects due to the addition of lead to the binary magnesiumcopper alloys are obtained in general in alloys containing from about 0.5 to 15 per cent of cop'- per to which has been added from about 0.5 to 20 per cent of lead. The amount of improvement depends on the relative percentages of copper and lead and on the condition of the alloy, whether cast, heat treated, or wrought. I have also discovered that additional improvements in properties and in corrosion resistance can be obtained by adding certain percentages of tin and/or zinc to these ternary magnesium-copper-lead alloys. Such quaternary and quinary magnesium alloys may contain' from about 0.5 to 15 per cent of cop- 0.5 to 20per cent of lead, from about 0.5 to 10 per cent of tin, and from about 0.5 to 10 per cent of zinc. For many purposes I prefer to use an alloy containing 80 per cent or more of magnesium and 20 per cent or less of total added metals.

The following examples serve to illustrate the property improvements obtainable in these magnesium-copper-lead alloys. A casting alloy containing 2 per cent of copper had the following properties- Tensile strength lb./sq.in 12,200 Yield strength lb./sq.in 5,100 Elongationv per cent 3 The addition of lead in amounts varying from 3 to 8per cent gave alloys with the following improved properties:

Tensile strength lb./sq.in 113,500-165,700 Yield strength lb./sq.in 5300-5300- Elongation per cent 3.0-4.7

Similar property improvements were likewise Application .lanuary 13, 1937, Serial No. 120,426

2 Claims. (em. vses) percentage elongation and impact toughness of assignor to The Midland, Mich; a corobtained in the higher percentage copper alloys. For example, a binary magnesium-copper alloy containing 6 per cent of copper had the following properties:

Tensile strength lb./sq. in 18,800 5 Yield strength 1b./sq.in 8,700 Elongation per cent 2.9

The addition of 2 to 6 per cent of lead gave the following improved properties: 10

Tensile strength lbs./sq.in 20,500-21,200 Yield strength lbs. /sq. in 9,500-9,800 Elongation per cent 3.5-4.5

The additional property improvements obtained by adding at least one or" the low melting metals, tin and zinc, to the above described ternary magnesium-copper-lead alloys are exemplified by the following illustrations. A ternary magnesium alloy containing 2 per cent of copper and 8 per cent of lead had a yield strength of 5,900 pounds per square inch and a Brinell hardness of 37.0. The addition of 2 and 4 per cent of tin raised these values to 6,400 and 7,200 pounds per square inch respectively and to 38.1 and 42.2 Brinell hardness respectively. Another ternary magnesium alloy containing 6 per cent of copper and 6 per cent of lead had a yield strength of 9,800 pounds per square inch and a Brinell hardness of 41.1.' The addition of 3, 5, and 8 per cent of tin raised these values to 10,400, 12,600, and 13,000 pounds per square inch respectively, and to 42.8, 46.9, and 48.4 Brinell hardness respectively. In another instance, a quaternary magnesium alloy containing 2 per cent of copper, 8 per cent of lead. and 4 per cent of tin had a yield strength of 7,200

pounds per square inch and a Brinell hardness of of zinc raised these properties to 8,700, 9,200, and 11,300 pounds per square inch respectively, and to 44.3, 45.6, and 48.9 Brinell hardness respectively. Again, the ternary magnesium alloy containing 2 per cent of copper and 2 per cent of lead had a tensile strength of 12,400 pounds per square inch, a yield strength of 5,200 pounds per square inch, and a Brinell hardness of 35.9. The addition of 8 per cent of zinc raised these properties to 22,600 pounds per square inch, 8,600 pounds per square inch and a Brinell hardness of 44.3 respectively. Similar property improvements were likewise obtained in alloys containing higher percentages of copper and/or lead.

Many of the specific alloy compositions falling within the scope of this invention are amenable to heat treatment. A solution heat treatment (S. H. T.) consisting of 16 hours for example, produced a marked most of the alloys. Improvements amounting to 20-300 per cent were obtained, the amount r- This can be illustrated by the following examples:

Mg+2Cu+4Pb+8Zn Sand S. P. Property cast S. H. T.

N Tensile strength. lb./sq. in 21, 200 28, 400 28, 200 Yield strength lb./sq. in. 8, 500 8, 100 16, 100 ElongatioL per cent 4. 2 8. 3 3.0 Impact toughness i't.-lb 2. 9 8. 9 4. 3 Brinell hardness 44. 3 44. 0 56. 5

Mg+2Cu+8Pb+4Sn+8Zn-- Sand S. P Property cast S. H. T. T

Tensile strength lb./sq. in 19, 900 26, 600 30, 300 Yield strength i .lb./sq. in 11, 300 10, 300 21, 600 Elongationhmu per cent 1.9 5. 5 1.6 Impact toughnes ft.- 1.3 5. 6 2.2 Brincll hardness... 48. 9 49. 4 66. 8

I have likewise discovered that the corrosion resistance magnesium-copper-lead alloys may be still further improved by the addition of at least one of the metals, tin and zinc.

nesium-copper-lead alloys by the beneficial effect due to the presence of lead.

It has likewise been discovered that the corrosion resistance of the new ternary magnesiumcopper-lead alloys can be the addition of small amounts of at least one of the low melting metals, tin and zinc.

425 C Aging or precipitation heat treatment may be conducted for 18 to 24 hours at to C. Extruded shapes are produced by die be employed.

I particularly point out and distinctly claim as my invention:

1. An alloy consisting of from about 0.5 per 2. An alloy consisting of from 2 to 10 per cent of copper and from 2 to 10 per cent of lead, the balance being magnesium.

JOHN A. GANN.