A metal-matrix composite material includes a matrix having magnesium in an amount of more than about 0.3 weight percent but no more than about 2.5 weight percent, an alloying element of about 0.8 to about 2.5 weight percent iron or from about 1.0 to about 2.5 weight percent manganese, and the balance aluminum and impurities. Dispersed throughout the matrix is a plurality of metal oxide particles present in an amount of more than about 5 volume percent but no more than about 25 volume percent of the total volume of the matrix and the particles. This material may be cast into casting molds. After casting is complete and during solidification of the matrix alloy, a high volume fraction of intermetallic particles is crystallized in the matrix alloy. The total of the volume fractions of the metal oxide particles and the intermetallic particles is from about 10 to about 40 volume percent, preferably from about 25 to about 40 volume percent.