Microstructure, mechanical properties and strengthening mechanism of in-situ synthesized TiC/6061 nanocomposites

In-situ synthesized 1 wt%, 3 wt% and 5 wt%TiC/6061 nanocomposites were prepared by the reaction using Al-K₂TiF₆-C as starting materials. Microstructure, mechanical properties and strengthening mechanism of the nanocomposites were investigated. SEM observation illustrates the in-situ synthesized ceramic TiC particles show shape of a polygon and its average size is 60 nm. TEM results show that the interface between the Al matrix and TiC reinforcement is clear and no reaction products can be found. Grain refining can be observed in the composites, as the TiC content increased from 0 wt% to 3 wt%. However, grain coarsening appears in the 5 wt%TiC/6061 composites. As increasing the TiC content from 0 wt% to 5 wt%, the mechanical properties of the composites increase firstly and then decreases. The Vickers hardness, yield strength, tensile strength and elongation of the as-cast 3 wt%TiC/6061 composites achieve the maximum value of 80.7 HV, 135 MPa, 202 MPa and 15.3 %, respectively. Strengthening mechanisms of the TiC/6061 nanocomposites is the micromechanical strengthening mechanisms. As the TiC content increasing, CTE strengthening plays an important role.