US1797851A - Aluminum-base alloy - Google Patents

Description

Patented Mar. 24', 1931 UNITED STATES PATENT OFFICE THEODORE W. BOSSERT, OF NEW KENSINGTON, AND JOSEPH A. NOCK, JR., OF TAREN- TUM, PENNSYLVANIA, ASSIGNORS T ALUMINUM COMPANY OF AMERICA, OF PITTS- B'O'RGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA ALUMINUM-BASE ALLOY No Drawing.

The invention relates to aluminum base alloys, by which is meant throughout this specification, and in the appended claims, alloys containing aluminum in amounts greater than about 90 to 95 per cent.

Phe adaptability of aluminum alloys to use in various shapes and forms is determined in part by two factors, the workability of the alloy and the strength and stiffness of the J final product. One factor modifies the other, and often the production of a fabricated arti- ('le of certain strength and stiffness is precluded by the fact that an alloy capable of developing those certain properties is not capable of being mechanically formed or worked into the desired shape. On the other hand, an alloy which will Withstand the working operation may not be capable of developing the required strength and stiffness in the finished article.

An object of the invention is to provide an aluminum base alloy having such a oombination of useful properties as will meet the demand for a material of moderate cost, good mechanical properties, superior corrosion resistance, and an unusual adaptability to the ordinary methods of working, such as drawing, forging, swaging, extrusion, and the like.

A further and important object of the invention is to provide an aluminum base alloy from which an article of considerable strength and stiffness may be formed under severe metal-working conditions.

We have discovered that an aluminum base alloy containing manganese in amounts of from about 1 to 1.5 per cent, and magnesium in amounts of from about 0.5 to 1.5 per cent, possesses the general combination of desirable properties above mentioned, and, in addition thereto, is inherently capable of fabrication, under given metal Working conditions, into an article of greater strength and hardness than is usually obtainable with any known aluminum alloy of similar working characteristics.

The drawing and extruding characteristics of the new aluminum base alloy containing magnesium and manganese are equal or su perior to prior alloys of similar characteris- Application filed June 5, 1930. Serial No. 459,417.

tics, of which prior alloys an aluminum base manganese alloy containing 1 to 1.5 per cent of manganese is an example, such alloy having hitherto been considered to have excel lent adaptability to the types of working conditions herein contemplated. Under given metal-working conditions, the strength and stiffness of a finished article made from our new aluminum-manganese-magnesium alloy is greater than the strength and stiffness of articles made from known alloys of similar working characteristics, such as the aluminum base manganese alloy containing 1 to 1.5 per cent of manganese.

A further important property of our new alloy rests in' its resistance to static deformation under a constant and sustained load. This property, usually known as resistance to creep, is important wherever an article must support heavy loads over a Wide and comparatively unsupported area, as when, for

instance, corrugated sheet metal is so used for roofing that 1t must withstand the deformation caused by sustained and heavy stresses such as those produced by large amounts of snow. In this respect, our aluminum-magnesium-manganese alloy is superior to an aluminum-manganese alloy of the composition above mentioned. For instance, an aluminum alloy containing about 1.25 per cent of manganese, and in the form of a sheet strip 1 inch wide resting on supports 8 inches apart, was subjected to a constant and sustained load by placing a weight at a point midway between the supports, which load subjected the sheet to a maximum fibre stress of about 20,000 pounds per square inch. U11 der these conditions, the deflection from the horizontal which initially resulted from the application of the weight was increased 0.026 of an. inch in 30 minutes. Under these exact conditions, an aluminum base alloy embodying our-invention, and containing 1.25 per cent of manganese and 1 per cent of magnesium, exhibited an increase, from the deflection which initially resulted from the application of the load, of only 0.002 of an inch at the end of 30 minutes.

Within the limits of from about 1 to 1.5 per cent of manganese, the amount of that element may be varied without materially affecting the desirable properties of our aluminum base alloy. So also, the magnesium content may be varied between 0.5 and 1.5 per cent to produce alloys-of the nature contemplated by this invention. An aluminum base alloy containing 1.25 per cent of magnesium and 1.25

. per cent of manganese has the desired properties, as do alloys containing 1.25 per cent of manganese and 1 per cent of magnesium, and 1.5 per cent of manganese and 1.25 er cent of magnesium. We have found t at alloys containing as low as 0.5 per cent of magnesium together with 1 to 1.5 per cent of manganese also serve the purposes and produce the effects contemplated by our invention. However, the preferred alloys contain between about 1 to 1.5 per cent ofeach of the elements magnesium and manganese.

The mechanical properties of these new alloys vary according to the relative amounts of manganese and magnesium present, but the variation is not of great magnitude. For instance, the tensile strength vof alloys of the composition ranges above named does not, in the annealed or soft condition, deviate greatly from limits of about 22,000 to about 30,000

pounds per square inch. While the yield point of the same alloys is generally within a range of about 8,000 to about 10,000 pounds per square inch, the percentage elongation in 2 inches varies'between about 18 and 30 er cent. These properties, while not compara 1e with the pro rties of what are generally designated as t e strong aluminum alloys, are very favorable when the fact is considered thataluminum base alloys containing manganese and magnesium in accordance with this invention have working characteristics which are better than those alloys of equivalent or greater strength and hardness.

The alloys may be made from either commercial aluminum, which ma contain from about 0.4 per cent or more 0 im urities, or from aluminum of extremely high purity which may contain amounts as low as 0.02 per cent of impurities, but in either case, the desirable properties of the alloy are retained. In alloys of this general type, it is well known to add amounts of either iron or silicon or both, which elements are common impurities in the commercial aluminum. We have found that the beneficial effects obtained with loys embodying our invention are exceedingly resistant to the action of corrosive agents. For example, we have found that when samples of these alloys are subjected to the action of salt solutions, their resistance to corrosion is su erior to that of other aluminum alloys of ii e strength and hardness, and is also, surprisingly, somewhat su rior to that of the ordinary commercia aluminum.

According to the provisions of the patent statutes, we have ex lained the princi 1e of our invention, and ave given spec' c examples of its characteristics and properties. However, we desire to have it understood that, within the scope of the ap nded claims, the invention may be practiceditherwise than as herein specifically described and exemplified.

We claim as our invention:

1. An aluminum base alloy containing from about 1 to about 1.5 per cent of manganese and from about 0.5 to about 1.5 per cent of magnesium, the aluminum content being not less than about 95 per cent, and the alloy being free from other alloying constituents except those present as impurities.

2. An aluminum base alloy containing from about 1 to about 1.5 per cent of manganese, and from about 1 to about 1.5 per cent of magnesium, the aluminum content being not less than about 95 r cent, and the alloy being free from other a oying constituents except those present as im uritles.

In testimony w ereof, we hereunto sign our names.

THEODORE W. BOSSERT. JOSEPH A. NOCK, JR.

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