Abstract: This invention provides a process which permits impurity-free sound Mg-based composite materials and Mg alloy-based composite materials to be efficiently and inexpensively produced without pressurizing a melt of matrix metal and without using a metal oxide, finely divided metal or metal fluoride. Specifically, it provides a process for producing an Mg-based composite material or an Mg alloy-based composite material which comprises replacing the gas within a mass of reinforcing material (9) by a non-protective gas, and bringing at least a part of the mass of reinforcing material (9) into contact with a melt (7) of Mg or Mg alloy so as to infiltrate the melt (7) into the mass of reinforcing material (9).

Abstract: The present invention relates to a process for producing a Mg-based composite material by using Mg or a Mg alloy as the matrix and utilizing a spontaneous infiltration phenomenon. This process comprises the step of bringing a powder mixture composed of a reinforcing agent and a infiltration agent into contact with a molten matrix metal comprising Mg or a Mg alloy, so as to cause the molten matrix metal to infiltrate into the powder mixture. The present invention also relates to a process for producing a Mg-based composite material which comprises the steps of forming a preform composed of a reinforcing agent and a infiltration agent and causing a molten matrix metal comprising Mg or a Mg alloy to infiltrate into the preform.