A composite has a magnesium base metal matrix and a reinforcing phase. The composite is produced from a charge containing a rapidly solidified magnesium base alloy and particles of a reinforcing material present in an amount ranging from about 0.1 to 50 percent by volume of the charge. Ball milling the charge energetically enfolds metal matrix material around each of the particles, while maintaining the charge in a pulverant state. Consolidation of the charge provides a mechanically formable, substantially void-free mass.