Spark plasma sintering of B4C and B4C-TiB2 composites: Deformation and failure mechanisms under quasistatic and dynamic loading |
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Authors: | WS Rubink V Ageh H Lide NA Ley ML Young DT Casem EJ Faierson TW Scharf |
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Affiliation: | 1. Materials Science and Engineering and Advanced Materials and Manufacturing Processes Institute (AMMPI), University of North Texas, Denton, TX, 76203, USA;2. Impact Physics Branch, Weapons and Materials Research Directorate, CCDC Army Research Laboratory, Aberdeen Proving Ground, MD, 21005, USA;3. Quad City Manufacturing Laboratory, Western Illinois University, Rock Island, IL, 61299, USA |
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Abstract: | Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B4C and various B4C-TiB2 compositions. SPS allowed for consolidation of pure B4C, B4C-13 vol.%TiB2, and B4C-23 vol.%TiB2 composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB2 phase in both small and larger-scaled composites. An optimized B4C-23 vol.%TiB2 composite with a targeted low density of ~3.0 g/cm3 exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B4C matrix in compression and TiB2 phase in tension, and c) TiB2 phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB2 serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor. |
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Keywords: | Spark plasma sintering Boron carbide - titanium diboride Fracture toughness Kolsky bar flexural bend strength Electron microscopy |
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