Although ceramics have many advantages when compared to metals in specific applications, they could be more widely applied if their low properties (fracture toughness, strength, and electrical and thermal conductivities) are improved. Reinforcing ceramics by two nano-phases that have different morphologies and/or properties, called the hybrid microstructure design, has been implemented to develop hybrid ceramic nanocomposites with tailored nanostructures, improved mechanical properties, and enhanced functionalities. The use of the novel spark plasma sintering (SPS) process allowed for the sintering of hybrid ceramic nanocomposite materials to maintain high relative density while also preserving the small grain size of the matrix. As a result, hybrid nanocomposite materials that have better mechanical and functional properties than those of either conventional composites or nanocomposites were produced. The development of hybrid ceramic nanocomposites is in its early stage and it is expected to continue attracting the interest of the scientific community. In the present paper, the progress made in the development of alumina hybrid nanocomposites, using spark plasma sintering, and their properties are reviewed. In addition, the current challenges and potential applications are highlighted. Finally, future prospects for developing alumina hybrid nanocomposites that have better performance are set.

Large number of pre-mature failure cases of spline half-shafts of loader automobile rickshaws were encountered by an industry in Lahore, Pakistan. Unexpected fracture of the spline-region of half-shafts were reported shortly after the shafts were put to service. This paper presents the findings of a systematic investigation that was carried out to find the root cause of the failure. Visual inspection, mechanical characterization, microstructural analysis, and chemical composition analysis were used to study the failure. It was revealed that the failure was torsional fatigue fracture in nature, with crack initiating from one of the machining marks present near the spline-root. Main cause of failure was found to be stress concentration at machine marks present on the surface, especially the ones closer to spline-roots, resulting in crack initiation. Moreover, other factors like presence of manganese sulfide (MnS) inclusions and improper material had also contributed towards crack propagation and final fracture.