Abstract: A composite material mixture of free flowing reinforcement particles in a molten metal is solidified at a cooling rate greater than about 15.degree. C. per second between the liquidus and solidus temperatures of the matrix alloy. This high cooling rate imparts a homogeneous structure to the solid composite material. Care is taken to avoid the introduction of gas bubbles into the molten composite material while the mixture is stirred to prevent segregation of the particles. For viscous melts, an artificial surface layer such as a fiberglass blanket may be used to prevent entrapment of bubbles during pre-casting stirring. Additionally, gas bubbles are removed from the molten mixture by filtering and skimming.

Abstract: A composite material mixture of free flowing reinforcement particles in a molten metal is solidified at a cooling rate greater than about 15.degree. C. per second between the liquidus and solidus temperatures of the matrix alloy. This high cooling rate imparts a homogeneous structure to the solid composite material. Care is taken to avoid the introduction of gas bubbles into the molten composite material while the mixture is stirred to prevent segregation of the particles. For viscous melts, an artificial surface layer such as a fiberglass blanket may be used to prevent entrapment of bubbles during pre-casting stirring. Additionally, gas bubbles are removed from the molten mixture by filtering and skimming.

Abstract: A cast composite material is prepared from a modified aluminum-containing matrix and reinforcement particles mixed into the matrix. From about 15 to about 130, preferably from about 20 to about 50, parts per million of an element, preferably beryllium, that forms a more stable oxide than magnesium oxide is included in the matrix alloy. The stable-oxide-forming element reduces the amount and thickness of the aluminum oxide and other oxides formed at the surface of the melt, which otherwise may be mixed into the melt to cause microstructural irregularities in the matrix of the cast composite material.

Abstract: A cast composite material is prepared from a modified aluminum-containing matrix and reinforcement particles mixed into the matrix. From about 15 to about 130, preferably from about 20 to about 50, parts per million of an element, preferably beryllium, that forms a more stable oxide than magnesium oxide is included in the matrix alloy. The stable-oxide-forming element reduces the amount and thickness of the aluminum oxide and other oxides formed at the surface of the melt, which otherwise may be mixed into the melt to cause microstructural irregularities in the matrix of the cast composite material.