Abstract: A preform for a composite material which has high strength and excellent air permeability and hence is applicable to a high-speed die casting method and which is capable of forming a metal composite material having excellent mechanical properties by a high-speed die casting method. Also provided is a process for producing such a preform. Ceramic fibers or/and ceramic particles are mixed with a silica sol and calcium carbonate and sintered at a predetermined temperature to form a calcium/silicon sinter obtained from the silica sol and calcium carbonate. The calcium/silicon sinter coats the ceramic fibers or/and ceramic particles so that a preform having the fibers or/and the particles bound to each other by the calcium/silicon sinter is obtained. The preform for a composite material has high strength and excellent air permeability and is applicable to the high-speed die casting method capable of attaining high productivity.

Abstract: A metal composite material is obtained by casting a melt of a metal and has an outer surface on which aluminum borate particles maintained in a porous form are exposed. Therefore, an oil is allowed to infiltrate the aluminum borate particles on the outer surface, to be retained therein and to ooze out during sliding. As a consequence, the sliding life during which desired sliding properties are maintained can be significantly prolonged. The metal composite material may be produced from a preform obtained by sintering aluminum borate particles covered with electrically neutralized silica and alumina particles which have been formed by mixing a silica sol and an alumina sol with aluminum borate particles in an aqueous solution to cover aluminum borate particles.

Abstract: A metal composite material which can show high wear resistance and durability when used as a sliding member and a process for producing such a metal includes material are proposed. The metal composite material (10) comprises a porous preform (1) containing porous aluminum borate particles (3) in which pores (3a) of the aluminum borate particles (3) are filled with a metal as a result of impregnation of a melt of the metal into the porous preform under pressure. In the metal composite material (10), the metal base material and the aluminum borate particles (3) are tightly bound to each other. Therefore, the metal composite material (10) has high strength and hardness and can show excellent wear resistance when used as a sliding member.

Abstract: A preform for a composite material which has high strength and excellent air permeability and hence is applicable to a high-speed die casting method and which is capable of forming a metal composite material having excellent mechanical properties by a high-speed die casting method. Also provided is a process for producing such a preform. Ceramic fibers or/and ceramic particles are mixed with a silica sol and calcium carbonate and sintered at a predetermined temperature to form a calcium/silicon sinter obtained from the silica sol and calcium carbonate. The calcium/silicon sinter coats the ceramic fibers or/and ceramic particles so that a preform having the fibers or/and the particles bound to each other by the calcium/silicon sinter is obtained. The preform for a composite material has high strength and excellent air permeability and is applicable to the high-speed die casting method capable of attaining high productivity.