Process for preparation of composite materials containing nonmetallic particles in a metallic matrix, and composite materials made thereby

A method for preparing a composite of a metallic alloy reinforced with particles of a nonmetallic material, comprising:

• forming a mixture of the molten metallic alloy and the particles;
• maintaining the mixture in a temperature range of from about the liquidus temperature of the metallic material to a temperature whereat the particles do not substantially degrade during the time required for the subsequent processing steps;
• mixing together the particles and the molten metal for a time sufficient to wet the molten metal to the particles and to distribute the particles throughout the molten metal, using a rotating dispersing impeller immersed in the molten mixture to shear the particles and the molten metal past each other while minimizing the introduction of gas into the mixture and while minimizing the retention of gas already present in the mixture, said step of mixing to occur with a vacuum applied to the mixture;
• and
• casting the resulting mixture.

A method for preparing a composite of a metallic alloy reinforced with particles of a nonmetallic material, comprising:

• forming a mixture of the metallic alloy and the particles in a crucible, under vacuum, and at a temperature above the liquidus of the metallic alloy;
• mixing together the particles and the molten metal with an impeller which is positioned below the surface of the melt and which is operated to avoid a vortex at the surface of the melt, said step of mixing to occur at a temperature above the liquids of the metallic alloy and for a time sufficient to wet the molten metallic alloy to the particles and to distribute the particles throughout the molten metallic alloy, with a vacuum applied to the molten mixture;
• and
• casting the resulting mixture.