TiB 2 films were deposited on silicon wafers and AISI M2 steel substrates by pulsed dc close field unbalanced magnetron sputtering. The samples were annealed in an inert argon atmosphere at 673, 873 and 1073 K for 1 h. The structural changes due to annealing were evaluated using X-ray diffractometry and scanning electron microscopy. The mechanical properties of the films were characterised by microhardness and scratch tests. The microstructure, microhardness and adhesive strength of the films varied depending on the annealing temperature. While it was observed that the hardness and adhesion strength of TiB 2 films annealed at 673 K improved, these properties decreased for the films that were annealed at higher temperatures.
Small amount of TiB2 (<5 wt%) was added into B4C through a novel method that combines the use of sputter deposition and hot pressing. Sputter deposition provided more uniform dispersion of TiB2 grains with smaller grain sizes as compared to the conventional particulate mixing. Small amount TiB2 addition demonstrated to be an effective way for improving the fracture behavior and toughness of B4C while not sacrificing its outstanding lightweight property to a large extent: 2.3 wt% TiB2 addition brought 15% improvement in indentation fracture toughness while resulting in less than 2% increase in density. The improvement can be attributed to the combination of crack impeding by TiB2 grains and crack deflection at the B4C–TiB2 interfaces. TiB2 also played as grain growth inhibitor resulting in a slight increase (2%) in Vickers hardness. Another intention of employing sputter deposition was to modify the grain boundary of B4C; however, neither formation of Ti‐containing phase nor Ti segregation has been observed at grain boundaries likely due to the poor wettability of B4C.
Over the last two decades, many studies have contributed to improving our understanding of the brittle failure mechanisms of boron carbide and provided a road map for inhibiting the underlying mechanisms and improving the mechanical response of boron carbide. This paper provides a review of the design and processing approaches utilized to address the amorphization and transgranular fracture of boron carbide, which are mainly based on what we have found through 9 years of work in the field of boron carbides as armor ceramics.
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