Nanoceramic composites with duplex microstructure break the strength-toughness tradeoff
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2020年第23期
论文作者：Ji Zou Hai-Bin Ma Jing-Jing Liu Wei-Min Wang Guo-Jun Zhang Zheng-Yi Fu
摘 要：There is a strength and fracture toughness tradeoff in nanoceramic composite. The strength varies reciprocally with the grain size whereas the toughness contributed by compressive residual stress increases with the dimension of the second phase. In this work, a novel duplex microstructure with reinforced clusters composing of nanosized grains was proposed and validated using a model system of B4C-TiB2 ceramics densified by carbide boronizing. As-obtained ceramics exhibit excellent combined mechanical properties at room temperature, including Vickers hardness, Young’s modulus, flexural strength and fracture toughness（by surface crack in flexure method） of 32.1 ± 2.7 GPa, 506.9 ± 2.0 GPa,1175 ± 71 MPa and 5.1 ± 0.4 MPa m0.5, respectively. Both strength and toughness are at least ～30 % higher than the counterparts with similar composition but homogenously distributed TiB2 grains. Graphite onion was confirmed to be an intermediate product during reactive sintering, it facilitated the grain pullout during fracture and retained the nanometric TiB2 grain in the cluster, both of which also contribute the toughening and strengthening mechanisms in the B4C-TiB2 ceramics.
Ji Zou1,2，Hai-Bin Ma3，Jing-Jing Liu1，Wei-Min Wang1，Guo-Jun Zhang4，Zheng-Yi Fu1
1. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology2. School of Metallurgy and Materials,University of Birmingham3. China Nuclear Power Technology Research Institute4. State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Institute of Functional Materials,Donghua University
摘 要：There is a strength and fracture toughness tradeoff in nanoceramic composite. The strength varies reciprocally with the grain size whereas the toughness contributed by compressive residual stress increases with the dimension of the second phase. In this work, a novel duplex microstructure with reinforced clusters composing of nanosized grains was proposed and validated using a model system of B4C-TiB2 ceramics densified by carbide boronizing. As-obtained ceramics exhibit excellent combined mechanical properties at room temperature, including Vickers hardness, Young’s modulus, flexural strength and fracture toughness（by surface crack in flexure method） of 32.1 ± 2.7 GPa, 506.9 ± 2.0 GPa,1175 ± 71 MPa and 5.1 ± 0.4 MPa m0.5, respectively. Both strength and toughness are at least ～30 % higher than the counterparts with similar composition but homogenously distributed TiB2 grains. Graphite onion was confirmed to be an intermediate product during reactive sintering, it facilitated the grain pullout during fracture and retained the nanometric TiB2 grain in the cluster, both of which also contribute the toughening and strengthening mechanisms in the B4C-TiB2 ceramics.
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