From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Patent specification for the improvement of magnesium alloys using beryllium and zirconium.
| Identifier | ExFiles\Box 147\2\ scan0071 | |
| Date | 15th February 1938 | |
| HR ENCLOSURE Nº 959 "JUSTSO" 511,291 PATENT SPECIFICATION Convention Date (France): Feb. 16, 1937. Application Date (in United Kingdom): Feb. 15, 1938. No. 4694/38. Complete Specification Accepted: Aug. 16, 1939. COMPLETE SPECIFICATION Magnesium Alloys We, COMPAGNIE DE PRODUITS CHIMIQUES ET ELECTROMETALLURGIQUES ALAIS, FROGES ET CAMARGUE, of 23 rue de Balzac, Paris, France, a body Cor- 5 porate organized under French law, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the 10 following statement:— This invention relates to magnesium base alloys which contain beryllium. Magnesium base alloys are, as a rule, liable to oxidation, particularly in the 15 molten state, but also in the solid state at elevated temperatures, for example temperatures above 300° C. In order to obviate this liability to oxidation, it has been proposed to add 20 small percentages of calcium to magnesium base alloys. We have employed beryllium for this purpose, but have found that whilst this metal has the advantage over calcium of 25 suppressing the liability to oxidation much more efficiently, it has the disadvantage of causing certain magnesium base alloys, especially such as contain aluminium and/or zinc, to solidify with 30 an extremely coarse grain structure, with its usual attendant drawbacks such as low mechanical strength and fatigue resistance, and the lengthening of any heat treatment to which the alloys may subse- 35 quently be subjected. With magnesium base alloys containing zinc but no aluminium, this grain-coarsening is observable only when beryllium is incorporated in the alloys well in excess of the quantity 40 per se necessary to suppress the liability to oxidation. It has now been ascertained that the addition of zirconium to such magnesium base alloys in which, owing to the addi- 45 tion of beryllium, a coarsening of the grain structure takes place as compared with the same alloys containing no beryllium, has the effect of restoring to these alloys, to a substantial extent at least, 50 the property of forming on solidification a fine grain structure without in any way impairing the resistance to oxidation due to the presence of the beryllium. At the same time, the treatment with zirconium, by virtue of the fine grain structure result- 55 ing therefrom, avoids the undesirable reduction in mechanical properties imparted thereto by the presence of the beryllium, the mechanical strength properties being more equal to those of the 60 original metal or alloy containing neither beryllium nor zirconium. By way of example, beryllium can be present in the metal or alloys in amounts lying between 0.005 and 0.5% while 65 zirconium may be present in amounts lying between 0.005 and 0.5%. It has been found that a content of 0.025% of beryllium imparts to the alloy a sufficient resistance to oxidation for all 70 practical purposes. Based on the foregoing observations, the present invention provides a process for imparting to magnesium base alloys containing beryllium, in which the pre- 75 sence of beryllium causes the formation of a grain, on solidification, which is coarse as compared with the grain of similar alloys in which beryllium is absent, a finer grain structure and correspondingly 80 improved mechanical strength properties, which process comprises adding zirconium to such alloys when molten. The invention further contemplates alloys of the aforesaid type containing 85 beryllium, preferably in an amount lying between 0.005 and 0.5%, such alloys having by virtue of a treatment with zirconium of such alloys in the molten state, a refined grain and improved 90 mechanical strength properties, as compared with similar alloys, in the preparation or remelting of which zirconium has not been used. The zirconium can be added either in 95 making up the alloys or when remelting ingots or scrap. The zirconium may be introduced in any desired manner for example in the form of pre-alloys, or in the form of salts 100 of zirconium which are adapted to be reduced to metal in contact with the molten magnesium base alloys. The alloys of the present invention can even be melted without use of a flux. Due 105 to the decreased liability to oxidation of [Price 1/-] | ||