GB380577A - Process for modifying aluminium alloys containing silicon - Google Patents

Abstract

Aluminium silicon alloys containing 5-30 per cent of silicon are improved or modified by treating the molten alloy with mixtures comprising fluorides that per se are incapable of producing a modifying effect and alkali carbonates. Such stable fluorides comprise fluorides of alkaline-earth metals, aluminium, magnesium, heavy metals such as manganese, zinc, and double fluorides of alkali metals. The melting-point of the mixtures may be reduced by additions of salts or known fluxes such as alkali chlorides. Constituents of the alloys other than silicon, for example iron, copper, manganese, cobalt, &c., also become highly dispersed by the treatment. The process may be used as a pretreatment to known modifying processes for example, after adding the reaction mixture metallic sodium may be added to the melt through the flux. The treated alloys may be further subjected to mechanical or heat treatment. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the age-hardening of the treated alloys by annealing at temperatures above 400 DEG C., quenching and ageing at ordinary or elevated temperatures, and the use of borates as fluxes for lowering the melting temperatures of the reaction mixture. This subject-matter does not appear in the Specification as accepted.