Abdul Wadood

In the present work, 0.25 wt%GNP-Ti composites were prepared through powder metallurgy route by adopting three types of mixing modes to investigate the extent of mixing on the mechanical and tribological properties. Dry ball milling, wet ball milling, and rotator mixing were independently employed to homogenize the composite constituents. Three types of composite powders obtained were subsequently sintered into composite pellets by cold compaction followed by vacuum sintering. Morphological investigation of composite powders performed by SEM revealed better homogenization of GNPs in Ti matrix for dry ball milled composite powder, whereas wet ball milled and rotator mixed composite powders showed aggregation and bundling of GNPs. Micro Vickers hardness of composites produced via dry ball milling is 4.56% and 15.7% higher than wet ball milled and rotator mixed samples, respectively. Wear test performed by pin-on-disk tribometer showed higher wear loss for wet ball milled and rotator mixed composites in comparison to dry ball milled.

Aluminium matrix composites with high specific strength are attracting attention for use in automobile and aerospace applications. Graphene nanoplatelets (GNPs) were added in 0.1, 0.5, and 1 weight fractions to an Al6061 matrix. Spark plasma sintering was used with a combination of solution sonication and ball milling to disperse the GNPs in the Al6061 matrix. The evolution of the microstructure was studied using optical and scanning electron microscopy. The uniformity of the GNP distribution is discussed in light of selected ball milling parameters. Electron backscattered diffraction analysis was used to measure the grain size and misorientation. X-ray diffraction analysis and transmission electron microscopy revealed neat and clean interfaces between the matrix and GNPs. Hardness and tensile testing revealed a considerable increment in the strength of the final composite after addition of GNPs. Traces of GNP clusters were found in the 1 wt.% composite as well as premature failure at lower strain due to the insufficient load transfer capability of the Al6061-T6 matrix. An illustrative two-dimensional model was developed to explain the load transfer behavior and the deterioration of the mechanical properties.