Method for mixing particles into a liquid medium

A method for producing a metal matrix composite comprising the steps of:

• a) introducing a molten metal into a vessel, said molten metal at least partially filling said vessel so as to form a matrix surface and a matrix body;
• b) rotating an impeller disposed in said matrix body so as to create a shear region in said matrix body and under said matrix surface, wherein if said impeller comprises an impeller head in proximity to an impeller base such that rotation of said impeller head relative to said impeller base generates said shear region, wherein said impeller base projects upward from the bottom surface of said vessel, wherein said impeller head has a non-planar inner contour facing said impeller base and wherein said impeller base has an outer contour facing said impeller head that is complementary in shape and substantially parallel to said inner contour of said impeller head;
• and
• c) introducing nonmetallic particles into said matrix body under said matrix surface and within said shear region using solids pump means, said solids pump means for feeding said nonmetalic particles into said matrix body within said vessel.