DE1035912B - Magnesium alloys - Google Patents

Description

Magnesium alloys Magnesium-zinc alloys or magnesium-zinc-manganese alloys, which cerium in the pure state or in the form of mischmetal (rare earth metals) is added in order to avoid micro-cavities, are known. These alloys however, they are difficult to process, oxidize very easily, and tend to form coarse crystals and are very sensitive to the silicon content. When you look at these If alloys want to have few micropipes, you have to choose between very good mechanical Properties, but with micro-cavities (high content of zinc, low content of mischmetal), or poor mechanical properties, but without micro-shrinkage (low content zinc, high content of mischmetal).

Subject of the "inventions are alloys; which as far as possible are free from these defects. In addition, the special influences were the most important rare earth metals for the alloys mentioned are systematically examined in detail and of the well-known advantage of beryllium, namely the prevention of harmful effects Oxidation in heat, made use of.

It was found that among those that could be used industrially Rare earth metals practically pure, d. H. about 900/0 lanthanum the micro-cavities best eliminated or degraded.

According to the invention, almost pure lanthanum is used, preferably in an amount of 0.5 to 1.5%. It could also be determined that a Alloy with 60/0 zinc and an addition of lanthanum practically eliminates micro-shrinkage.

According to the invention, such a magnesium alloy has the following composition: zinc ............................ 6 to 70/0 lanthanum, practically pure, preferably ............ '* ..... **''"0.5 to 1.50 / 0 aluminum, preferably ......... 0.50 / 0 beryllium ....................... 0.010 / 0 silicon, at most ............... 0.150 / 0 magnesium ...................... as the remainder The aluminum facilitates the introduction of the beryllium into the alloy and, together with this, facilitates casting.

In the above alloys, the lanthanum can be made from rare earth metals with about 920/0 lanthanum, 40/0 neodymium and 40/0 praseodymium.

The mechanical properties of the above alloys, however, are somewhat weaker than with other rare earth metals because the zinc content is low.

According to the invention it has now been found that the rare earth metals best have the following composition : Praseodymium ......... ............. 10 to 15 ° / o Lanthanum ......................... 0 to 10 ° / o cerium ................... ....... 00/0 samarium .................. ..... 16 to 170/0 neodymium. . . . . . . . . . . . . . . . . . . . . . . . . as the rest. The rare earth metals are added in an amount of 0.5 to 20/0 to the magnesium-zinc-aluminum (0.50 / 0) -eryllium (0.010 / 0) alloys and give them better mechanical properties, even if the zinc content is low (50/0) and the rare earth metal content is high (e.g. 1.50 / 0).

A magnesium-zinc alloy according to the invention then has the following Composition: Zinc ............................ 5 to 70/0 rare earth metals above composition ....................... 0.5 to 20/0 aluminum, preferably ......... 0.50 / 0 beryllium ....................... 0.010 / 0 silicon, at most ...... ......... 0150/0 Magnesium ...................... as the remainder. This shows that in the Alloys of the invention allow a content of silicon that is ten times higher lies than the salary, as it was with the earlier, similar Alloys was allowed if good mechanical properties were to be obtained.

Finally, it can also be seen that the favorable properties by using rare earth metals of the above composition as well eliminate the difficulties previously caused by the zinc content.

The invention also includes heat treating the above Alloys. In the as-cast state, these alloys have the following mechanical properties Tensile strenght . . . . . . . . . . :. . . 17 to 20 kg / mm2 elastic limit. . . . . . . . . . . . 7 to 10 kg / mm 2 elongation .................... 4 to 80 / p dia direct homogenization, e.g. B: 12 hours at 460 ° C with subsequent tempering Good properties are obtained after 24 hours at 160.degree. C., but generally occurs a grain enlargement due to the heat treatment.

With gradual homogenization (12 hours at 338 ° C and 12 hours at 460 ° C), the grain enlargement is avoided: Likewise, a gradual Tempering, namely 24 hours at 140 ° C and 24 hours at 160 ° C, a higher one Maintains elongation despite high elastic limit. Such a heat treatment (two stages of homogenization and two stages of tempering) results in the following mechanical Properties tensile strength. . . . . . . . . . . . . . . . . 25 to 30 kg / mm2 elastic limit . ... . . . . . . . . . 16 to 20 kg / mmq elongation .................... 5 to 100 / p

Claims (4)

PATENT CLAIMS: 1. Magnesium alloys, characterized in that they have the following composition: 5 to 70 / p zinc, 0.5 to 20 / p rare earth metals, 0.4 to 0.6% aluminum, 0.008 to 0.012 ° / o Beryllium, not more than 0.15% silicon, the remainder being magnesium, the rare earth metals being composed as follows: 10 to 15% praseodymium, 16 to 17% samarium, 0 to 10% lanthanum, 00 / p Cerium, remainder neodymium. 2. Magnesium alloys according to claim 1, characterized in that they have the following composition: 6 to 711 / p zinc, 0.5 to 1.511; p rare earth metals, 0.4 to 0.60 / p aluminum, 0.008 to 0.0120 / p beryllium, at most 0.150 / p silicon, The remainder is magnesium, with the rare earth metals consisting of at least 900 / p lanthanum. 3. Magnesium alloys. according to claim 2, characterized in that the rare Contains earth metals 920 / p lanthanum. 4. Process for the production of the magnesium alloys according to claims 1 to 3, characterized by a heat treatment in which for homogenization first to 338 ° C for 12 hours and then to about 12 hours 460 ° C, then cooled in the air and then at 120 bis for 24 hours 150 ° C and 24 hours at 140 to 200 ° C is tempered. Considered publications: German Patent No. 806 055; Excerpts from German patent applications, Vol. 19, Issue date May 4, 1948, p. 440.