GB652229A - Improvements in or relating to the production of magnesium base alloys - Google Patents

Abstract

Zirconium and beryllium are introduced into magnesium by means of a composition which is capable of introducing zirconium solubly into magnesium and which contains a reducible halide of beryllium such as beryllium fluoride or the fluoberyllate of an alkali metal. The ratio of zirconium to beryllium is preferably between 50 and 500 to 1. The composition, in addition to the beryllium halide may consist of an intimate fused anhydrous mixture of at least one of the chlorides of barium and/or strontium and zirconium chloride, the mixture containing at least 15 per cent of barium chloride or at least 20 per cent of strontium chloride or a mixture of the two in amounts equivalent to 15 per cent barium chloride reckoning 1 per cent of strontium chloride to 0.7 per cent barium chloride, the mixture containing at least 4 per cent of zirconium. The composition may consist of zirconium fluoride mixed or combined with one or more fluorides of lithium, barium, strontium, calcium and magnesium, selected so as to be fluid at the alloying temperature, and beryllium halide. The composition may consist of beryllium and at least one of the following three phases: (1) a metallic matrix phase consisting mainly of magnesium and/or one or more "permissible elements" as defined below; (2) a metallic phase consisting mainly or wholly of zirconium and (3) a salt phase in quantity not exceeding 30 per cent of the whole and consisting mainly or wholly of one or more halides, the composition being substantially free from "zirconium alloying inhibitor elements" and containing at least 1 per cent of zirconium. The composition may consist of one or more chlorides of alkali and alkaline earth metals (including magnesium), together with mixtures or compounds of zirconium fluoride and sodium and/or potassium fluoride together with a beryllium halide. Any of the above compositions may contain up to 20 per cent of innocuous substances, i.e. compounds of zirconium or of "permissible elements" or such compounds of "zirconium alloying inhibitor elements" which do not give rise to these inhibitor elements in molten magnesium. "Zirconium alloying inhibitor elements" are defined as elements which form high melting point compounds with zirconium and thus precipitate zirconium from solution in magnesium-zirconium alloys. "Permissible elements" do not form such compounds and the most important of these elements are zinc, cadmium, cerium, silver, thallium, thorium, copper, bismuth, beryllium, lead and calcium. The production of magnesium-base alloys containing zirconium and beryllium may be performed by stirring the composition into magnesium or a magnesium base alloy in the absence of "zirconium alloying inhibitor elements" and casting the product into moulds. Specifications 511,137, 511,291, 652,222, 652,223, 652,227, and 652,230 are referred to.