B4C-SiC composites with tuneable mechanical properties: Role of Al2O3-Y2O3 sintering additives

While outstanding properties of boron carbide (B4C)-silicon carbide (SiC) composites make them potential candidates for ballistic and wear resistance applications, the applicability is rather limited due to processing challenges to obtain high density and superior mechanical properties. In the present work, B4C-10 wt% SiC composites are spark plasma sintered without additives and with 6 wt% (Al2O3-Y2O3) additives at 1600 degrees C, 1700 degrees C and 1800 degrees C. When sintered at 1600 degrees C, the relative density increased from 94% for the composites without additives to-99% with Al2O3-Y2O3 additives. The formation of liquid phase comprising Al-Y-Si-O improved density and mechanical properties of the composites. TEM analysis of the composite sintered with (2 wt% Al2O3 4 wt% Y2O3) additives at 1800 degrees C confirmed clean grain boundaries between B4C, SiC and liquid phase precipitates. When sintered at 1700 degrees C, the indentation fracture toughness increased from 4.3 MPa.m0.5 for the composite without additive to 6.0 MPa.m0.5 for the composite with 6 wt% Al2O3 additive due to increased instances of crack splitting, bridging and deflection.