Journal
CERAMICS INTERNATIONAL
Volume 44, Issue 9, Pages 10766-10772Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ceramint.2018.03.114
Keywords
Boron carbide; Fine-grained microstructure; Mechanical properties; Hot pressing; High-energy ball milling; Toughening mechanism
Categories
Funding
- National Natural Science Foundation of China [51702080, 61701164]
- Natural Science Foundation of Hebei Province [E2016402035, E2017402045]
- Science and Technology Research Development Program of Handan [1621211039, 1621211039-3]
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Dense and fine-grained boron carbide (B4C) ceramics were fabricated via high-pressure hot pressing (100 MPa) using powders, which are prepared by high-energy ball milling. These powders were sintered at a low temperature (1800 degrees C) without any sintering aid. The dense and fine-grained B4C ceramics demonstrate super high hardness, outstanding fracture toughness and modern flexure strength. The milled powders were characterised by disordered crystal structure and ultrafine particle size that ranges from a few nanometres to a few hundred nanometres. The combined contributions of high pressure and the characteristic of the milled powders guaranteed that the dense fine-grained microstructure was achieved at only 1800 degrees C. The grain size distribution of the ceramics was inhomogeneous and ranged from 70 nm to 1.6 mu m. However, the average grain size was fine at only 430 nm, which partially contributed to the super high hardness of the B4C ceramics. The locally concentrated areas of the small grains changed the fracture mode of the B4C ceramics from the complete transgranular fracture to a mixture of transgranular and intergranular fractures, thereby enhancing the toughness of the B4C ceramics. The relative density, Vickers hardness, flexure strength and fracture toughness of the obtained B4C ceramics reached up to 99.5%, 41.3 GPa, 564 MPa and 4.41 MPa m(1/2), respectively.
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