GB652222A - Improvements in or relating to the production of magnesium alloys - Google Patents

Abstract

A master alloy, for use in the production of magnesium base alloys containing zirconium, comprises at least the following three phases: (1) a metallic matrix phase consisting mainly of magnesium and/or one or more "permissible elements" and having zirconium dissolved therein; (2) a metallic phase consisting mainly or wholly of zirconium in readily alloyable form and (3) a salt phase in quantity between 1 and 30 per cent of the whole and consisting mainly or wholly of one or more halides inert to molten magnesium; the master alloy being substantially free from "zirconium alloying inhibitor elements" and containing at least three per cent zirconium. The "permissible elements" are defined in the Specification as elements which are incapable of combining with the zirconium dissolved in magnesium to form high melting point compounds which settle out. Among such elements are zinc, cadmium, cerium, silver, thallium, thorium, copper, bismuth, beryllium, lead, calcium. "Zirconium alloying inhibitor elements" are elements which do form such high melting point compounds. The master alloy may be made by mixing an excess of molten magnesium with a molten or prefused substance consisting of a zirconium halide with or without other suitable halides under conditions permitting reduction of the zirconium halide to produce metallic zirconium but incapable of permitting any substantial incorporation of zirconium in the excess magnesium which is poured off. The said substance may consist solely of fluorides. The mixing may take place in vacuo or in an inert atmosphere. A magnesium-base alloy may be produced by introducing the master alloy into molten magnesium and agitating it therein. Specifications 511,137, 511,482, 533,264, 652,223, 652,230 and 26438/39 (as open to inspection under Sect. 91) are referred to.