The bending strength temperature dependence of the directionally solidified eutectic LaB6-ZrB2 composite
The bending strength temperature dependence of the directionally solidified eutectic LaB6-ZrB2 composite
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DOI：
10.1016/j.jallcom.2011.02.176
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发表时间：
2011-05-19
影响因子：
6.2
通讯作者：
Loboda, P.
中科院分区：
文献类型：
--
作者：
Bogomol, I.;Nishimura, T.;Loboda, P.
采用基于压制粉末无坩埚区熔的悬浮区熔法制备了定向凝固LaB 6-ZrB 2共晶。以ZrB_2和LaB_6粉末为初始材料。复合材料的弯曲强度在25-1600 ℃的温度范围内进行了评估，在1600 ℃时达到950 MPa。通过残余应力分析、断裂韧性测试以及断口扫描电镜和透射电镜观察，研究了不同条件下的增韧机理。我们推测LaB 6-ZrB 2共晶在25-1200 ℃的强度主要与裂纹偏转、桥韧机制和ZrB 2相塑性的增加有关;在1200-1600 ℃的强度主要与基体和纤维塑性的增加有关。通过对纤维位错结构的分析，揭示了ZrB 2单晶在高温变形过程中发生的应变硬化。确定了定向凝固LaB 6-ZrB 2共晶在1600 ℃附近从脆性断裂模式到韧性断裂模式的变化。(C)2011 Elsevier B. V.保留所有权利。
A directionally solidified LaB6-ZrB2 eutectic was prepared by the floating zone method based on the crucible-free zone melting of compacted powders. ZrB2 and LaB6 powders were used as the initial materials. The bending strength of the composite was evaluated in the temperature range of 25-1600 degrees C and reached 950 MPa at 1600 degrees C. Using a residual stress analysis, fracture toughness, and SEM and TEM fracture investigations, the toughening mechanisms under different conditions were studied. We speculate that the strength of the LaB6-ZrB2 eutectic at 25-1200 degrees C is mainly associated with crack deflection, bridge toughening mechanisms and increasing plasticity of the ZrB2 phase; and at 1200-1600 degrees C, with the increasing plasticity of the matrix and fibers. By analyzing the dislocation structure of the fibers, the occurrence of strain hardening in the single crystalline ZrB2 during high-temperature deformation was revealed. The change from the brittle to ductile fracture mode for the directionally solidified LaB6-ZrB2 eutectic at near 1600 degrees C was determined. (C) 2011 Elsevier B.V. All rights reserved.