US2882145A - Magnesium alloys - Google Patents

Description

United States Patent MAGNESIUM ALLOYS Ren Lucien, Neuilly-sur-Seine, and Emile Tetart, Louvie-Juzon, France No Drawing. Application December 28, 1955 Serial No. 589,351

Claims priority, application France December 28, 1954 1 Claim. (Cl. 75-168) (Filed under Rule 47(a) and 35 U.S.C. 116) Percent Neodymium 10 to 50 Lanthanum -l 20 to 75 Praseodymium 5 to 15 Samarium 1 to 17 Cerium less than The same patent also indicates that, taking into account the reaction efficiencies in the reduction of the salts of rare earths by the magnesium, the most favorable results as far as the hot and cold mechanical character-- istics are concerned, are obtained when the final composition of the rare earths in the alloy is as follows:

Percent Neodymium 40 to 65 Lanthanum 25 to 35 Praseodymium 8 to 12 Samarium 0.5 Cerium 2 to 10 On the other hand, it is well known that the introduction of zirconium in the magnesium produces an excellent fineness of grain and improves the mechanical characteristics of the alloy. This effect of zirconium is particularly notable in alloys of magnesium with rare earths.

With the adding of zirconium in the known proportions, that is to say from 0.1 to 1%, to the alloys of magnesium and rare earths referred to above, products might have been expected which had optimum characteristics. Experience has shown, however, that this is not at all the case. There is indeed found a very considerable refinement of grain with excellent characteristics in the rough-cast state or after homogenization by thermal treatment, but the alloys thus obtained do not withstand tempering treatment at 200 to 300 centigrade; after these treatments, their characteristics fall off to a very considerable extent, and this is clearly undesirable in the case of alloys required to be effective while hot.

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The applicants have found, on the other hand, and this is the object of the present invention, that very low contents of zirconium such as, for example, in the order of from 0.01 to 0.05%, in the magnesium-rare earths alloys considered never give rise to a weakness during tempering or heat treatment. However, on the other hand, zirconium in the low contents indicated no longer causes a refinement of the grain and, consequently, there is obtained no improvement in mechanical characteristics. This, however, is without importance since, by virtue of the particular composition of the rare earths, the alloy has adequate characteristics. It should be mentioned that, in the case of castings of alloys of this kind and containing 0.01 to 0.05% of zirconium, a greater homogeneity of the alloy has been noted together with the almost complete disappearance of segregations. This is of the utmost importance to the physical characteristics of such parts and completely eliminates the slight degradation to which the elongations of certain massive zones of these parts are sometimes subjected.

The addition of zirconium under the conditions contemplated by the invention does not modify the special thermal treatment of the alloy.

The following sets forth the alloy percentages according to the invention:

Rare earth metals percent 2-6 Zirconium ..do 0.01-0.05 Magnesium the remainder the composition of the rare earth metals being as follows:

Percent 25-35 8-12 Lanthanum Praseodymium Cerium 2-10 Samarium 0.5 Neodymium the remainder, 40-65 What we claim is: Alloys of magnesium with rare earth metals and zirconium, having the following composition:

Rare earth metals percent 2 to 6 Zirconium ..do 0.01 to 0.05 Magnesium the remainder and in which the composition of the earth metals in the final alloy is as follows:

Percent Lanthanum 25 to 35 Praseodymium 8 to 12 Cerium 2 to 10 Samarium 0.5 Neodymium the remainder, 40 to 65 References Cited in the file of this patent OTHER REFERENCES Journal of Metals, vol. 1, issue 12, pages 968-983, December 1949.