In situ production of ceramic reinforcement in metallic parts by thermal degradation of organometallics

Abstract

The ability to enhance the physical and mechanical properties of metallic components by particulate ceramic reinforcement is well documented. Several methods have been used to incorporate the ceramic particles in the metallic matrix. These methods can be classified into three groups based on the physical state of the metallic phase during processing: (1) liquid phase methods, (2) solid state methods and (3) semi-solid state methods. Liquid phase methods have generated considerable interest because they offer the most economical route for the production of near-net-shape components. In order to realize the full benefits of the ceramic reinforcement, it is imperative that the interfacial bond strength between the ceramic and the metal be maximized. This interfacial bond strength depends to a large extent on the ability of the molten metal to wet the ceramic. It is often difficult to achieve good wetting between molten metals and ceramics because of the large surface tension commonly associated with metals. Several techniques have been used to improve metal/ceramic wetting characteristics. These methods include application of coatings on the ceramic, alloying the metal with reactive elements such as Li, Mg, Ca, Ti or Zr and heat treating the ceramic. A variety of new technologies are alsomore » emerging for the in situ production of the reinforcing phase. The in situ production of the ceramic could potentially enhance the wetting characteristics and may probide improved control of the size and level of reinforcement. In this contribution, the feasibility of producing ceramic reinforcements in situ by thermal degradation of a suitable organometallic in a liquid metal bath has been explored.« less