Comparison between axial residual stresses measured by Raman spectroscopy and X-ray diffraction in SiC fiber reinforced titanium matrix composite
Comparison between axial residual stresses measured by Raman spectroscopy and X-ray diffraction in SiC fiber reinforced titanium matrix composite
复制标题
SiC纤维增强钛基复合材料拉曼光谱与X射线衍射测量轴向残余应力的比较
DOI：
10.7498/aps.67.20181157
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发表时间：
2018-10
影响因子：
1
通讯作者：
Wen Mao
中科院分区：
文献类型：
--
作者：
Huang Hao;Zhang Kan;Wu Ming;Li Hu;Wang Min-Juan;Zhang Shu-Ming;Chen Jian-Hong;Wen Mao
准确测量和分析SiCf/Ti复合材料的残余应力状态对于优化其制备工艺和了解其失效模式是至关重要的，但这仍然是一个挑战。在本工作中，用涂覆纤维的方法制备了纤维体积分数为48%的SiCf/C/Ti17复合材料，该复合材料由直径约100m的W芯碳化硅纤维、厚度约2.5m的涡流层C涂层和Ti17基体组成，通过在920℃/120 Mpa/2 h的热等静压工艺制备了纤维体积分数为48%的SiCf/C/Ti17复合材料，并对其进行了应力测试。结果表明，涡流层C涂层是碳化硅纤维与Ti17合金之间必需的扩散阻挡层，承担着纤维与基体在固结过程中由于热膨胀系数失配而产生的残余应力。高倍率电子显微镜观察发现，涡流层C涂层中的石墨烯平面几乎平行于碳化硅纤维的轴向，因此C涂层的G峰位置对应力状态很敏感。为此，首次利用显微拉曼光谱测量了SiCf/C/Ti17复合材料中C涂层在应力状态和无应力状态下的G峰位置。根据残馀应力引起的G带位置移动，计算出SiCf/C/Ti17复合材料中碳化硅纤维的轴向残馀压应力为~705.0 Mpa。为了进行对比，还采用X射线衍射法测量了Ti17合金基体在不同方向上的晶面间距，得到了空间应变。在测量过程中，选择了-Ti(213)高角衍射峰来减小测量误差，然后在=0、45和90三个不同方向上改变的值，得到了不同的-Ti(213)晶面间距值。采用三轴应力模型时，SiCf/C/Ti17复合材料轴向的残余拉应力约为701.3 Mpa，通过线弹性理论转化为碳化硅纤维的残余压应力约为759.4 Mpa。结果表明，用拉曼光谱和X射线衍射法表征含高织构涡轮层状碳的SiCf/C/Ti17复合材料的残余应力是可靠的。
Accurate measurement and analysis of residual stress state in the SiCf/Ti composites are crucial to optimizing their fabrication process and to understanding their failure mode, but they are still a challenge. In this work, SiCf/C/Ti17 composites with~48% fiber volume fraction, consisting of W-core SiC fibers (~100 m in diameter), turbostratic C coating (~2.5 m in thickness) and Ti17 matrix, are prepared by consolidating precursor wires fabricated by matrix-coated fiber method through hot isostatic pressing at 920℃/120 MPa/2 h; these samples are used for measuring their stresses. It is noted that turbostratic C coating, a necessary diffusion barrier layer between SiC fiber and Ti17 alloy matrix, bears the residual stress caused by the mismatch of thermal expansion coefficients between fiber and matrix during consolidation. It is found that the graphene planes are almost parallel to the axial direction of SiC fibers in the turbostratic C coating revealed by high magnification transmission electron microscope, and thus G peak position of C coating would be sensitive to stress state. Accordingly, micro-Raman spectroscopy is first used to measure the G peak positions of C coating under stress and stress-free state in the SiCf/C/Ti17 composite, respectively. Based on the position shift of G band caused by residual stress, the axial residual compressive stress of SiC fiber in SiCf/C/Ti17 composite is calculated to be~705.0 MPa. For comparison, X-ray diffraction method is also adopted to measure the interplanar spacing values of the Ti17 alloy matrix in different directions to obtain the spatial strains. During measurement, -Ti (213) high-angle diffraction peak is chosen to reduce test error, and then the different interplanar spacing values of -Ti (213) are obtained by varying the values of in three different directions at =0, 45 and 90. As three-axis-stress model is employed, the residual tensile stress of Ti17 alloy matrix in the axial direction of SiCf/C/Ti17 composite is~701.3 MPa, which is transformed through linear elastic theory into the residual compressive stress of SiC fiber of~759.4 MPa. The similar results confirm that it is reliable to characterize the residual stress in the SiCf/C/Ti17 composite with high-texture turbostratic carbon by both the Raman spectroscopy and the X-ray diffraction method.