A new method for bonding metal matrix composite inserts during casting

Abstract

A new method, termed cast welding, has been developed for metallurgically bonding inserts into a cast component during a normal casting operation. This circumvents problems associated with squeeze casting or infiltrating a final component; composite inserts can be made previously, the component size is not limited, and costs are reduced. Experiments have proved the ability to bond an aluminium or zinc alloy matrix composite insert into an aluminium or zinc alloy cast component during either gravity casting or die casting. These inserts have a sound continuous metallurgical bond with an actual intermixture of the metal at the mating surface while leaving the composite reinforcement intact. The applicability to other alloy systems or insert types can be derived on the basis of fundamental bonding mechanisms. Laboratory tests have proved the effectiveness of cast welding simple geometries. Bonded tensile specimens have failed in the cast material away from the bond area. Production trials using complicated shapes have had encouraging results, but a number of difficulties must be considered in order to go into full-scale production: composite inserts must be sound and not outgas during casting, dies with more than one insert must be designed to have a similar temperature and flow condition at each insert location, and suitable non-destructive testing methods must be used to control the final component's fitness for service.