Volumetric strains were measured in silicon carbide/silicon carbide melt‐infiltrated ceramic matrix composites (CMCs) at ambient and high temperatures using high‐energy synchrotron X‐ray diffraction (XRD). Both silicon and silicon carbide constituents were interrogated utilizing a broad spectrum of diffracting planes that would be largely inaccessible to common laboratory XRD equipment. Residual room‐temperature principal strains in the melt‐infiltrated silicon phase were found to be approximately 1100 με in compression, corresponding to stresses of approximately 300 MPa using simplifying constitutive assumptions. Residual room‐temperature principal strains in silicon carbide particles found throughout the matrix were approximately 500 με in tension, corresponding to approximately 300 MPa. Residual strains were found to decrease considerably as temperatures increased from ambient temperature to 1250°C. Residual strains returned to approximately preheat treatment values after cool‐down to ambient temperature. Strain measurements in the silicon phase were found to be significantly affected by dissolved boron dopant levels causing contraction of the silicon lattice. This contraction must be accounted for in high‐temperature experiments for accurate calculation of stresses in the silicon phase.

中文翻译：

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高能X射线衍射对SiC / SiC陶瓷基复合材料热处理过程中残余应力演变的原位表征

使用高能同步辐射X射线衍射（XRD）在环境温度和高温下测量了碳化硅/碳化硅熔渗陶瓷基复合材料（CMC）的体积应变。硅和碳化硅成分都利用了宽范围的衍射平面进行了询问，而这是普通实验室XRD设备无法获得的。使用简化的本构假设，发现熔体渗透硅相中的室温残余残余主应力约为 1100με，对应于约300 MPa的应力。在整个基质中发现的碳化硅颗粒中的室温残余主应变约为 500με张力大约相当于300 MPa。发现随着温度从环境温度升高到1250°C，残余应变将大大降低。冷却至环境温度后，残余应变恢复到大约热处理前的值。发现在硅相中的应变测量受溶解的硼掺杂剂水平的显着影响，导致硼硅晶格收缩。为了准确计算硅相中的应力，必须在高温实验中考虑该收缩。