C - Chemistry – Metallurgy – 22 – C
Patent
C - Chemistry, Metallurgy
22
C
C22C 49/00 (2006.01) B22D 19/14 (2006.01) C22C 1/10 (2006.01) C22C 49/02 (2006.01)
Patent
CA 2317149
A process for making a low volume fraction preform for a metal matrix composite, wherein the metal is typically magnesium, aluminum and alloys thereof , and the reinforcement comprises either whiskers, fibres, tow or particulate, typically chosen from silicon carbide, graphite, carbon, silica, alumina, titanium diboride, boron nitride and boron carbide. The resulting preform has sufficient strength both to be handled, and to be infiltrated with liquid metal, for example by a squeeze casting process. A particular selection of binder material and sacrificial fillers is used to make the preform. In the first step, the reinforcement is mixed with a binder, and with sacrificial fillers, to provide a castable slurry which is then placed in a mould, to provide a green cast preform. In the second step, the green casting is dried, to remove any water and/or solvent remaining from the castable slurry. In the third step, the green preform is fired at a relatively low temperature, to burn off the sacrificial fillers. In the fourth step, the green preform is fired at an elevated temperature sufficiently high to sinter the binder to bond the reinforcement together. In the third and fourth steps particular combinations of temperature and time are used to ensure decomposition of the sacrificial fillers, followed by firing of the binder to sinter it and thus bond the preform together without destruction or cracking of the green preform. This process can also be used to provide low volume fraction preforms, so that the metal matrix composite contains less than about 8% by volume of whiskers, or less than 15% by volume of particulates.
Lo Jason Sin Hin
Santos Raul
Her Majesty In Right Of Canada As Represented By The Minister Of
Shapiro Cohen
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