Mechanical properties and deformation mechanisms of B4C–TiB2 eutectic composites

Samples of B4C–TiB2 eutectic are laser processed to produce composites with varying microstructural scales. The eutectic materials exhibit both load dependent and load independent hardness regimes with a transition occurring between 4 and 5 N indentation load. The load-independent hardness of eutectics with a microstructural scale smaller than 1 μm is about 31 GPa, and the indentation fracture toughness (5–10 N indenter load) of the eutectics is 2.47–4.76 MPa m1/2. Indentation-induced cracks are deflected by TiB2 lamellae, and indentation-induced spallation is reduced in the B4C–TiB2 eutectic compared to monolithic B4C. Indentation-induced amorphization in monolithic B4C and the B4C phase of the eutectic is detected using Raman spectroscopy. Sub-surface damage is observed using TEM, including microcracking and amorphization damage in B4C and B4C–TiB2 eutectics. Dislocations are observed in the TiB2 phase of eutectics with an interlamellar spacing of 1.9 μm.