GB907404A - Shaped articles of light metals or their alloys and process for their production - Google Patents

Abstract

A process for the production of shaped articles of a light metal, and particularly magnesium, aluminium or their alloys, having a fine micro crystalline structure, is characterized in that fine particles of the light metal which contain in dispersed form fine crystallites of a solid insoluble metal phase are heated to a temperature within the range of plastic deformation of the light metal or alloy and ram-extruded with a substantial reduction in cross-sectional area, e.g. at least 80% of the compacted mass. The grain structure of the light metal article is heterogeneous due to the presence of a finely divided crystalline metallic phase which is, at room temperature, insoluble in the light metal matrix and which is uniformly dispersed throughout the shaped article. The aluminium or magnesium alloy contains at least 70% aluminium or magnesium respectively and the solid insoluble metallic phase corresponds to from 0.05 to 20% by volume based on the total volume of the light metal. The fine particles of the light metal or alloy thereof are prepared by atomizing an alloy of the light metal to which has been added a small proportion of a metal or of an alloy thereof which is soluble in the melted or liquefied light metal but which is insoluble or only slightly soluble, preferably no more than 0.1% by weight, in the solidified light metal, such as gold, barium, beryllium, rare earth metals, palladium, platinum, antimony, selenium, strontium, tellurium, thorium, uranium, cobalt, germanium or silicon. In an aluminium or aluminium alloy is distributed a solid insoluble metal phase of one or more of the metals gold, barium, beryllium, cerium, palladium, platinum, antimony, selenium, strontium, tellurium, thorium, uranium or an intermetallic compound of these metals with aluminium, e.g. AnAl2, BaAl4, CeAl4, PdAl3, SbAl, Se3Al2, Sr0Al4, Te3Al2, ThAl3 and UAl4. In a magnesium or a magnesium alloy is distributed one or more of the metals barium, cobalt, germanium, antimony, silicon, strontium or of an intermetallic compound of these metals with magnesium, e.g. Mg9Ba, Mg2Co, Mg4Ge, Mg3Sb2, Mg2Si and Mg9Sr. It is essential that the solidification of the atomized alloy takes place quickly in order to minimize aggregation or crystal growth of constituents which are insoluble in the solidified light metal. To ensure this the molten metal is subjected to a dispersion and chilling operation to obtain fine individually frozen discrete particles. The atomized metal is heated between 290 DEG and 510 DEG C. for magnesium alloys and between 260 DEG and 510 DEG C. for aluminium base alloys in preparation for compacting and die extrusion. Specification 662,312 is referred to.