Indentation deformation and microcracking in β-Si ₃N ₄-based nanoceramic

The effects of microstructure on the mechanical responses and damage evolution of spark-plasma-sintered β-Si ₃N ₄-based ceramics has been evaluated through indentation tests. It was found that the nanoceramic and its coarse-grained counterpart exhibit similar elastoplastic behavior in their indentation responses. However, the increased hardness and ratio of elastic work to total work done in the nanoceramic suggest that resistance to plastic deformation is greater than that in the coarser-grained one. The microcracking behavior within the indented materials is also proposed. A finite-element analysis is used to estimate the distribution of compressive and shear stresses within the indented materials. The smaller grain size in bridging ceramic not only enhances the energy dissipation by formation of a higher density of intergranular microcracks along the weak grain boundary phase but also toughens the cracked solid through increasing resistance to plastic sliding and multi-cracks propagation. Prior to formation of the radial cracks, better damage tolerance of nanoceramic is thought to be achieved in this study.