Strength and toughness: The challenging case of TaC-based composites
Strength and toughness: The challenging case of TaC-based composites
复制标题
DOI：
10.1016/j.compositesb.2014.11.043
复制
发表时间：
2015-04
影响因子：
13.1
通讯作者：
L. Silvestroni;L. Pienti;S. Guicciardi;D. Sciti
中科院分区：
文献类型：
--
作者：
L. Silvestroni;L. Pienti;S. Guicciardi;D. Sciti
本工作旨在研究碳化钽（TaC）陶瓷，用于航空航天和能源生产部门的耐火陶瓷的强度和韧性之间的关系。探索了不同第二相的影响：（I）添加具有合适热弹性性质的过渡金属硅化物TaSi 2，（II）添加SiC颗粒、薄片或纤维，以及（III）短切碳纤维。微观结构分析，通过扫描和透射电子显微镜进行，是必不可少的，在纳米级揭示在烧结过程中发生的形态变化，在增强相及其与基体和烧结添加剂的相互作用。相应地提出了强化演化的机制。断裂韧性和弯曲强度进行了测量，并进行了比较，以未增强的材料和讨论的微观结构特征协议的值。当加入SiC颗粒时，获得了接近1GPa的强度，但残余热应力阻止了韧性的显著增加，韧性在4 MPa·m左右波动。发现添加Hi-Nicalon SiC纤维时，强度和韧性之间有很好的折衷，分别为550 MPa和5.3 MPa/m。由于基体中的拉伸状态升高，较多的耐火SiC纤维不能起到有效的作用。另一方面，TaSi 2导致4.7MPa μ m的韧性和约680 MPa的强度。相反，碳纤维由于与基体的热膨胀系数的不利组合而导致较差的韧性。
This work aims at studying the relationships between strength and toughness of tantalum carbide (TaC) ceramics, a refractory ceramic used in aerospace and energy production sectors. The effect of different secondary phases was explored: (I) the addition of a transition metal silicide with suited thermo-elastic properties, TaSi2, (II) the addition of SiC particles, platelets or fibers, and (III) chopped carbon fibers. Microstructural analyses, performed by scanning and transmission electron microscopy, were essential in revealing at nanoscale level the morphological changes occurred during sintering in the reinforcing phase and its interaction with matrix and sintering additive. Mechanisms of reinforcement evolution are suggested accordingly. Fracture toughness and flexural strength were measured and the values were compared to unreinforced materials and discussed in agreement to the microstructural features. Strength approaching 1 GPa was obtained upon addition of SiC particles, but residual thermal stresses prevented from notable increase of toughness, which fluctuated around 4 MPa √m. A good compromise between strength and toughness was found for addition of Hi-Nicalon SiC fiber, 550 MPa and 5.3 MPa √m, respectively. More refractory SiC fibers resulted not effective, owing to the rising of tensional state in the matrix. On the other hand, TaSi2led to a toughness of 4.7 MPa √m and strength around 680 MPa. Conversely, carbon fiber led to poor toughness due to unfavorable combination of coefficient of thermal expansion with the matrix.