US1676856A - Alloy - Google Patents

Description

July 10, 1928.

' A. G. C. GWYER ET AL ALLOY Original Filed July 18, 1925 4:05 amt-005 006 1:07 -oo8 009 0| -cll -ol2 INCHES.

Patented July 10, 1928.

UNITED STATES PATENT OFFICE.

ALFRED GEORGE COOPER GWYER AND HENRY WILFRED LEWIS PHILLIPS, OF LONDON,

, ENGLAND, ASSIGNORS TO THE BRITISH ALUMINUM COMPANY, LJiMITED, OF LON- DON, ENGLAND.

ALLOY.

Original application filed July 18, 1925, Serial No. 44,535, and in Great Britain July 19, 19241. Divided and this application filed August 26, 1926.

This invention deals with matter divided from application No. 44,535 filed on July 18th 1925and relates to the improvement of the structure of alloys of the aluminiumcopper series, that is to say, alloys mostly composed of aluminium (or in which the aluminium content is of the order of about 50 per cent, such alloys being referred to hereinas mostly composed of aluminium) lates.

The invention consists in a method of modifying or physically varying the struc-- ture of an aluminium alloy containing a substantial proportion of copper, for example up to about 14 per cent, although this figure may be considerably exceeded and may be as high, for exam le, as about 54: per cent, with or without ot er metals comprising the addition to the molten alloy of a small quantity of an alkaline earth metal.

The invention also consists in the processes for modifying or physically varying the structure of aluminium alloys containing A substantial proportions of copper as herein Serial No. 131,742.

etched with ferric nitrate and magnified to the same scale as Figure 1.

In the original photomicrographs from which the illustrations have been drawn the grain is finer and more uniform than shown in the drawings.

In carrying the invention into effect in the form illustrated by way of example in Figures 1 and 2, we modify the structure of an aluminium-copper alloy composed of aluminium 88% and copper 12%.

The change in micro-structure is not great but the order of change can be seen in the drawings. a

The modifier which in this example is 0.2 per cent of calcium is added to the molten alloy while the latter is at a temperature of about 800 C. The constituents appear to be the same as in the corresponding Figures 1 and 2 but the difference in structure is not so striking as in those figures. The

changes which are brought about in aluminium-copper alloys, though important from a practical standpoint, are not necessarily associated with very marked changes in structure, thus rendering investigation difiicult, more especially as the results of tensile tests, for example of alloys made on the laboratory scale. may not be consistent.

As a further example the following is g1ven:-

An alloy composed of aluminium 92 per cent and copper 8per cent was modified by the addition to the melt at 750 C. of 0.3 per cent of calcium. The improvement of the structure was such that an increase in percentage elongation of about 30 per cent was secured.

We find there is an optimum quantity of modifying agent to employ for best results. An experiment in any given case will readily show this quantity. the structure usually improving progressively up to an addition of a certain proportion, after which reversion or deterioration appears to set in.

Experiments made on an alloy composed of aluminium 92 per cent and copper 8 per cent with calcium as a modifying agent and successive increases of 0.1 per cent from nothing to 0.5 per cent showed that the optimum value in the case of that test was chosen being that of percentage elongation.

The invention is not limited to the particular composition of aluminium-copper alloy given above nor to the particular moditying agent.

Modifiers may be added in any suitable way to the melt, for example, by wrapping them in aluminium foil. In some cases, especially if they are maintained below the surface of the melt, for example when calcium is wrapped in aluminium foil, no visible signs or indications of reaction occur.

Another method of adding the modifier is by way of an alloy. In the case of calcium this may comprise an alloy containing 92 per cent aluminium and 8 per cent calcium or an alloy containing 98 per cent aluminium and 2 per, cent calcium. Such alloys are brittle and can be easily broken up with a hammer, after which they may be added to the melt in small quantities.

Preferably the operation of casting the alloys modified according to the present invention should be carried out either in chill moulds or in sand moulds provided with suitable chills so as to accelerate the rate of'solidification of the metal in the heavier portions of the castings.

The alloys should not be held long in the molten condition after the addition of the modifier.

The invention includes ternary or other alloys of aluminium containing substantial proportions of copper, for example aluminline earth metal we mean barium, stront-ium, or calcium.

We claim- 1. The method which consists in the addition to a molten alloy containing at least about 6% of copper and at least about of aluminium of about 0.1 to 0.3% of an alkaline earth metal.

2. A method of physically varying the structure of aluminium alloys containing above about 6% of copper and above about 50% of aluminium which comprises the addition to the molten alloy of an alkaline earth metal.

3. A method of physically varying the structure of aluminium alloys containing above about 6% of copper and above about 50% of aluminium which comprises the addition to the molten alloy of calcium.

4. Alloys prepared by the method claimed in claim 2.

5. The method which consists in the addition to a partially modified molten alloy containing at least about 6% of copper and at least about 50% of aluminium of an alkaline earth metal.

In testimony whereof we have signed our names to this specification.

ALFRED GEORGE COOPER GWYER. HENRY Will-RED LEWIS PHILLIPS.

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