Modification of Aluminum Alloys to Create in-situ Surface Composites

Engineered aluminum surface metal matrix composites were created by incorporating ceramic particles like WC, SiC, Al ₂ O ₃ , WC + SiC and mixture of hard particle with solid lubricant SiC + MoS ₂ , e.g., using friction stir processing. Processing parameters were studied and optimized to produce uniform distribution of these particles in the near surface region. Optical and scanning electron microscopy showed that the stirred region developed as deep as the pin probe. Proper tooling enables the thickness of surface zone to be controlled from thin to orders of magnitude thicker than conventional coatings. The composite is nearly defect free and forms a graded metallurgical bond with the underlying surface. No interface is developed between the composite zone and the base material. Study of properties such as hardness of the discontinuously reinforced surface composite, micro structural stability, wear resistance, wetting and other mechanical properties showed commendable increase. Volume fraction, particle size & properties and process parameters were observed to have major effect on the resulting material property. Control over the aforementioned variables was achieved leading to creation of surface metal matrix composites by design.