Aluminium lithium (Al-Li)-Silicon carbide (SiC) composites by powder metallurgy (PM) route

Aluminium-lithium (Al-Li) alloys have gained prominence in the aerospace industry in recent years as structural materials. This is due primarily to their mechanical properties, such as high specific strength and modulus, and low density. Development of Al-Li/ceramic composites is currently being investigated to enhance the higher service capabilities of this material. Processing of Al-Li/ceramic composites by the powder metallurgy (PM) route offers many advantages over ingot casting such as a well-dispersed reinforcement distribution and easy handling. However, the PM route suffers from agglomeration of the ceramic reinforcement when the particle size is below 2.5 μm. This paper reports the development of several methods of mixing submicron ceramic powders with Al-Li to obtain a uniform distribution of the reinforcement. Among the methods used were mixing in a fluidized bed, ball milling, spray drying and mixing the metal powder with a ceramic slurry. The results showed that the methods employed in ceramic processing such as the uses of deflocculants are important to the success of mixing the submicron ceramics to Al-Li.