Correlation between phase evolution, mechanical properties and instrumented indentation response of TiB2-based ceramics
Correlation between phase evolution, mechanical properties and instrumented indentation response of TiB2-based ceramics
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DOI：
10.1016/j.jeurceramsoc.2008.06.030
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发表时间：
2009-02-01
影响因子：
5.7
通讯作者：
Suri, A. K.
中科院分区：
文献类型：
--
作者：
Mukhopadhyay, Amartya;Raju, G. B.;Suri, A. K.
在非氧化物高温陶瓷致密化过程中，如二硼化钛(TiB_2)，助烧剂的种类和用量直接影响着陶瓷的显微组织和力学性能。从这一角度出发，本工作旨在评估添加MoSi2(高达10wt.%)是否可以潜在地改善TiB2的力学性能(硬度、断裂韧性、弯曲强度)，同时增强TiB2的致密化行为。为了回答这样一个重要的问题并了解导致力学性能变化的机制，我们评估了一系列热压TiB2-MoSi2复合材料的尖锐仪器压痕响应(2N载荷)。此外，还分析了在宏观载荷(高达100N)下获得的维氏压痕数据。实验结果表明，在TiB2中加入2.5wt.%MoSi2，在1700℃热压后可获得较高的烧结密度(~gt；99%Rho(Th))。致密的TiB2-2.5wt.%MoSi2复合材料具有良好的综合力学性能，包括高硬度(H-v5接近30 Gpa)和中等断裂韧性(类似于6 Mpa m(1/2))。此外，四点。复合材料的弯曲强度在370-400 Mpa范围内变化，当MoSi2含量为2.5wt.%时，弯曲强度最大。有趣的是，添加剂(MoSi2)的含量增加到5wt.%以上会降低力学性能。力学性能的下降归因于第二相(Ti5Si3，Mo5Si3)的存在，并对其影响进行了严格的分析。用深度传感仪器维氏压痕仪记录的力学响应数据根据所做的弹塑性功进行了分析，根据卸载曲线的初始斜率计算的弹性模量(E)值在460-500 GPA范围内变化。此外，对宏观维氏硬度测量的分析揭示了“压痕-尺寸效应”，该效应已从压痕区域的机械响应以及与材料性能的相关性方面进行了讨论。(C)2008爱思唯尔有限公司。保留所有权利。
In densifying non-oxide high temperature ceramics, like titanium di-boride (TiB2), the type and amount of sinter-aid critically determine the microstructural developments and consequently the mechanical properties. In this perspective, the present work is carried out to assess the feasibility whether MoSi2 addition (up to 10 wt.%) can potentially improve the mechanical properties (hardness, fracture toughness, flexural strength), while enhancing the densification behaviour of TiB2. In order to answer such an important issue and to understand the mechanisms contributing to the variations in mechanical properties, we have evaluated sharp instrumented indentation response (2 N load) of a range of hot pressed TiB2-MoSi2 compositions. In addition, the Vickers indentation data obtained at macro load (up to 100 N) are also analyzed. Our experimental results reveal that the addition of only 2.5 wt.% MoSi2 to TiB2 results in the attainment of high sinter density (> 99% rho(th)), after hot pressing at 1700 degrees C. The dense TiB2-2.5 wt.% MoSi2 composite composition has been found to possess a good combination of mechanical properties, including high hardness (H-v5 similar to 30 GPa) and moderate fracture toughness (similar to 6 MPa m(1/2)). Furthermore, the four-point. flexural strength values vary in the range of 370-400 MPa, with the maximum value for 2.5 wt.% MoSi2 containing composite. Interestingly, an increase in the additive (MoSi2) content above 5 wt.% degrades the mechanical properties. The degradation in mechanical properties has been attributed to the presence of secondary phases (Ti5Si3, Mo5Si3) and its effect has been critically analyzed. The mechanical response data, recorded using depth sensing instrumented Vickers indenter has been analyzed in the light of the elastic/plastic work done, and the elastic modulus (E) values, as computed from the initial slopes of unloading curves, have been found to vary in the range of 460-500 GPa. Additionally, the analysis of macro Vickers hardness measurements reveal 'indentation-size effect', which has been discussed in terms of mechanical response at the indented zone, and in correlation with the material properties. (c) 2008 Elsevier Ltd. All rights reserved.