The addition of small quantities of rare-earth elements may have strong effects on the structure and properties of the solvate metal For example, when La is added into an Al matrix composites, the thermal resistance increases strongly due to the formation of an Al-La intermetallic compound At the same time as a result of a refinement of the grain size of the Al matrix, the comprehensive mechanical properties are improved and the anticorrosive property is also increases When a rare-earth element is added to Mg alloys, the mechanical properties, thermal resistance and processing properties improve, so that the scope of application of Mg alloy can be expanded into a matrix of composites In the case of nano scale Mg-Y composites reinforced by in-situ intermettallic compound particulates, which is a recent development, the elongation is greatly improved as a result of the fineness reinforcing particles is very fine, and the high temperature strength and anti-corrosive properties are also good