Mechanical properties and deformation mechanisms of B_4C-TiB_2 eutectic composites

摘要

Samples of B_4C-TiB_2 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 m~(1/2). Indentation-induced cracks are deflected by TiB_2 lamellae, and indentation-induced spallation is reduced in the B_4C-TiB_2 eutectic compared to monolithic B_4C. Indentation-induced amorphization in monolithic B_4C and the B_4C phase of the eutectic is detected using Raman spectroscopy. Sub-surface damage is observed using TEM, including microcracking and amorphization damage in B_4C and B_4C-TiB_2 eutectics. Dislocations are observed in the TiB_2 phase of eutectics with an interlamellar spacing of 1.9 μm.