Improvement of microstructure and strengthening mechanism in TiC particle reinforced aluminum matrix composites via copper nanocoating

Ball milling activated TiC particles (TiC p ) were coated with a Cu layer by electroless plating to improve their wettability and dispersity in Al matrix. The Cu coated TiC p (TiC p @Cu) reinforced Al matrix composites were fabricated via stir casting followed by hot extrusion. Scanning and transmission electron microscope analyses revealed that the coating consisted of Cu nanoparticles was tightly adhered on TiC p , whose uni-form dispersion refined the Al grains. The studies on the microstructure and tensile properties showed that numerous θ' nanorods and shells were precipitated in the matrix and on the TiC p @Cu/Al interface after the diffused reaction of Cu coating in Al. The θ' precipitates not only caused Orowan strengthening, but enhanced the loads transferred to the θ' nanorods and TiC p via their anchored TiC p @Cu/Al interface. When the TiC p content rose from 0 to 7 wt%, the composites tensile and yield strengths reached maxima of 156.5 and 109.6 MPa, which were 50.3 % and 70.5 % higher than those of the matrix, respectively. The strength improvements mainly resulted from the Orowan strengthening of the θ' precipitates and TiC p , and the load transfer strengthening of the θ' nanorods and θ' shell encapsulated TiC p @Cu. The stress dispersion effect of θ' nanorods and the retarded cracking of θ' precipitates anchored TiC p @Cu/Al interface slowed down the plasticity and elongation drops as the TiC p content rose from 0 to 5 wt%. The lower elongation at the 7 wt% TiC p addition arisen from a premature cracking at the agglomerated TiC p @Cu/Al interface under higher loads.