US2829970A - Beryllium containing nickel, manganese, copper alloys - Google Patents

Description

United States Patent 1 mil BERYLLIUM CGNTAINlNG NICKEL, MANGA- NESE, COPPER ALLOYS Application January 20, 1956, Serial No. 560,324 1 Claim. (Cl. 75-459) This invention relates to new and improved alloys containing nickel, manganese, copper and a predetermined small percentage of beryllium, and method of making the same.

Alloys of nickel, manganese and copper are used industrially and are in demand for applications in which non-ferrous, non-magnetic alloys are required having a hardness of Rockwell C45 or higher.

Alloys of these natures, however, reach their maximum hardness relatively slowly. For example, an alloy of nickel, 20% manganese and the balance copper, requires a period of approximately 24 hours to reach a maximum hardness in the vicinity of Rockwell C47. This is, of course, a serious industrial disadvantage.

It has been discovered that the addition of a relatively small percentage of beryllium, within a perscribed range of much smaller percentage than would be expected to produce any beneficial results or increase in hardness, to i a mixture of nickel, manganese and copper, not only unexpectedly and surprisingly greatly accelerates the age hardening process, but also increases the ultimate hardness. In other words, by adding a small percentage of beryllium to an alloy of nickel, manganese and copper not only is its hardness increased to and above an alloy not including beryllium, but the time required for obtaining a given fixed hardness is greatly reduced, and the requisite hardness more rapidly obtained in the beryllium containing alloy.

Since the small percentages of beryllium contemplated herein are insuflicient to produce precipitation hardening, the results produced, namely the increased hardness and accelerated age hardening, are wholly unexpected.

Accordingly, it is an object of the present invention to provide a new alloy consisting basically of nickel, manganese and copper to which a small percentage of beryllium has been added, which attains the same or greater hardness in a very much shorter time than is required for an alloy having the same percentages of nickel, manganese and copper without the beryllium added.

The following examples are given of alloys of nickel, manganese and copper having beryllium added thereto according to the present invention.

Example #1 -Alloy 849 Here an alloy was prepared containing Ni; 30% Mn; 0.38% Be and the balance Cu. In carrying out the melting operation, careful procedure is important to obtain a gas and oxide free casting. Preferably the melting operations in preparing the alloys are carried out by induction heating in a refractory, carbon-free crucible to avoid carbon contamination.

A second control alloy 848 was prepared without the Be, but having a 303 0-40 composition of NiMn Cu.

The alloys in each of the examples above were an nealed for two hours at 800 C. followed by a water quench before the aging treatment and were melted with no cover or flux.

Fig. 1 compares several alloys having 30% Ni30% MnCu composition with a range of added Be from 0 to 1.9%, as cast;

Fig. 2 compares some of the alloys in Fig. 1 when in cold rolled condition.

Fig. 1 shows the comparison between four different alloys having the same Ni, Mn and Cu relationships but with varying amounts of beryllium added. The alloy containing 0.38% beryllium is represented by the uppermost solid line and will be seen to attain a hardness of Rockwell C52 in approximately 52 hours of age hardening at the temperature specified. In comparison, the alloy containing no beryllium reaches, in the same time and under the same conditions a Rockwell hardness of about C48. However, what is more significant from this figure is the effect of greater percentages of beryllium on the alloys. For example, the Be alloy will be seen to have a hardness of about Rockwell (341.5 at the end of 1 hour of age hardening as compared to a hardness of about Rockwell C45 for the 38% Be alloy. Still greater additions of beryllium as represented by the 1.9% Be alloy show a tendency during the initial stages of age hardening to have a hardness very much less than the 38% Be alloy. Also, as will be seen the comparison of the three Be containing alloys during the first 4 hours of age hardening, the 38% Be alloy is the most desirable and in the initial stages of age hardening, the hardness is inversely proportional to the percentage of beryllium added. Thus, Fig. 1 graphically illustrates that about .38% Be is the maximum which should be employed. This is particularly true due to the high cost of beryllium and it will be readily appreciated that the dilference between .38% Be and, for example, .57% Be represents a 50% increase in the amount of beryllium in the alloy and a consequent proportional increase in the ultimate cost of the alloy.

Fig. 2 compares some of the alloys shown in Fig. 1 after being cold rolled 50% and this figure serves to show that particularly in the cold rolled condition, about 38% Be should be considered a practical maximum. The difference in ultimate hardness after cold rolling between the 38% and .85% Be alloys is much greater than the same alloys in the as cast condition as compared in Fig. 5. Therefore, particularly with the cold rolled alloy, the upper limit of about 38% Be should not be substantially exceeded.

Examination of the microstructure of the various suitable or acceptable alloys either with or without the beryllium shows no observable difierences. The appearance of the structure in each case is that of a single phase only. No precipitated phase is observed at magnification up to X1000. It is believed that the ordering of the lattice of the Mn-Ni-Cu alloys causes the setting up of strain centers in the surrounding matrix. The hardening is thus achieved by resistance to the movement of dislocations by these strain centers. Addition of solid solution hardness will then increase the strain set up in the areas where ordering occurs and, therefore, enhanced hardening is attained.

The various alloys were observed to have a Youngs modulus of about 25 X10 and hence are suitable for use as springs, etc.

We claim:

A substantially gas and oxide free alloy having improved age hardening characteristics which comprises approximately 30% nickel, 30% manganese, 38% beryllium, and the balance being substantially copper, said alloy having a hardness greater than Rockwell C50.

References Cited in the file of this patent UNITED STATES PATENTS 2,234,552 Dean et al Mar. 11, 1941 2,270,868 Dean et al. Jan. 27, 1942 2,289,593 Sawyer et al. July 14, 1942

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