Nanoceramic composites with duplex microstructure break the strength-toughness tradeoff
Nanoceramic composites with duplex microstructure break the strength-toughness tradeoff
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DOI：
10.1016/j.jmst.2020.05.014
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发表时间：
2020-06
影响因子：
10.9
通讯作者：
J. Zou;Hai-Bin Ma;Jing-jing Liu;Weimin Wang;Guo‐Jun Zhang;Z. Fu
中科院分区：
文献类型：
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作者：
J. Zou;Hai-Bin Ma;Jing-jing Liu;Weimin Wang;Guo‐Jun Zhang;Z. Fu
纳米陶瓷复合材料的强度和断裂韧性之间存在权衡。强度与晶粒度成反比关系，而残余压应力对韧性的贡献随第二相尺寸增大而增大。本文提出了一种新型的纳米颗粒增强团簇结构，并利用碳化物渗硼致密的B4C-TiB2陶瓷模型系统对其进行了验证。所制得的陶瓷具有优异的室温综合力学性能，其中维氏硬度为32.1±2.7 Gpa，杨氏弹性系数为506.9±2.0 Gpa，弯曲强度为1175±71 Mpa，断裂韧性为5.1±0.4 Mpa。其强度和韧性均比成分相近、颗粒分布均匀的TiB_2合金提高至少∼30%。在反应烧结过程中，石墨洋葱是一种中间产物，它促进了断裂时的晶粒拔出，并保留了团簇中的纳米TiB2颗粒，这也是B4C-TiB2陶瓷的增韧强化机制之一。
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-TiB2ceramics 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 TiB2grains. Graphite onion was confirmed to be an intermediate product during reactive sintering, it facilitated the grain pullout during fracture and retained the nanometric TiB2grain in the cluster, both of which also contribute the toughening and strengthening mechanisms in the B4C-TiB2ceramics.