PURPOSE: To enhance the mechanical properties and heat resistance of the resulting lightweight spring by using inorg. fiber such as ceramic fiber or metallic fiber having high elastic modulus and high strength as a reinforcing material for a metal matrix.

CONSTITUTION: As a reinforcing material aluminous fiber consisting of ≥ about 72wt% Al2O3 and ≤ about 28wt% SiO2 and practically showing no reflection of α-Al2O3 in the X-ray structure is used especially preferably. Such aluminous fiber has high tensile strength and high tensile elastic modulus. When aluminous fiber is used as a reinforcing material, a matrix metal used is required to have ≤ about 1,700°C m.p. in order to avoid the reduction of the high temp. strength of the fiber. A composite material consisting of the fiber and matrix metal is manufactured by liq. metal impregnation, powder metallurgy, deposition, plastic working or other method.