GB1444274A - Metal compositions - Google Patents

Abstract

1444274 Dispersed phases in alloys MASSACHUSETTS INSTITUTE OF TECHNOLOGY 3 Aug 1973 [7 Aug 1972] 37073/73 Addition to 1400624 Heading C7D [Also in Division B3] A metal or alloy which forms a dendritic structure when frozen from its liquid state without agitation, is agitated while in a liquid-solid state to convert the solid portion to primary solids comprising discrete degenerate dendrites and to prevent the formation of inter-connected dendritic networks, wherein third phase liquid or solid particles are added to the agitated metal or alloy and dispersed therein. The agitation of the liquid-solid mixture may be effected by counter rotating blades, electromagnetic stirring or gas bubbling. The third phase material may be added in steps, the composition being heated between each addition to increase the amount of secondary phase liquid present. This process may be continued until all the primary solids have been liquified. When the desired composition has been formed, it can be cooled to form an ingot which later may be re-heated until it attains a thixotropic state and then cast by forcing it into a die cavity. Alternatively, the composition, which comprises degenerate dendritic primary solids suspended in a secondary phase, the said secondary phase also having the said third phase particles dispersed therein, may be cast directly after the third phase material has been added to the mixture. The third phase material forms from 3-65 wt. per cent of the total composition, suitable materials including graphite, metal carbides, sand, glass, ceramics, metal oxides and metals. Suitable metals and alloys include Fe, Cu, Al, Pb-Sn, Zn-Al, Zn-Cu, Mg-Al, Mg-Al- Zn, Mg-Zn, Al-Cu, Al-Si, Al-Cu-Zn-Mg, Cu-Sn, Cu-Zn, super alloys, Co-Cr, steels, tool steels, stainless steels, and cast iron. Examples describe the preparation of compositions comprising an Al alloy containing 4.14%si and 1.8% Fl to which has been added one of the following: 10 or 20 wt. per cent of glass particles of 20 to 40 micron size, 20 wt. per cent of silicon carbide particles of 44 micron average size, 10 or 30 wt. per cent of aluminium oxide particles of 44 micron size, and 3 wt. per cent of titanium carbide particles of 1 to 5 micron size.