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结合仪器化微米划入和仪器化微米压入对(BNNT-BNNP)/(Zr B2-Si C)超高温陶瓷复合材料的形变强化效果及机理进行研究,并利用光学金相显微镜(OM)、冷场发射扫描电镜(SEM)和高分辨透射电镜(HR-TEM)分别对压痕和划痕、样品断口形貌及显微组织结构进行分析。结果表明,(BNNT-BNNP)/(Zr B2-Si C)超高温陶瓷复合材料具有显著的形变强化效应,且随着(BNNT-BNNP)含量的增多,复合材料的形变强化效果愈加明显。复合材料在放电等离子烧结制备的冷却阶段,因其组成相热膨胀系数的显著差异,导致Zr B2相内形成大量位错,且以固定位错为主。这些固定位错将阻碍可动位错的运动,使复合材料塑性变形的阻力增大,导致复合材料呈现明显的形变强化效应。
The effect and mechanism of deformation strengthening of (BNNT-BNNP) / (Zr B2-Si C) ultra-high temperature ceramic composites were investigated by means of instrumented micronization and instrumented microindentation. Optical and optical microscope (OM) Cold-field emission scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) were used to analyze the indentations and scratches, the fracture surface morphology and the microstructure of the samples respectively. The results show that (BNNT-BNNP) / (Zr B2-Si C) ultra-high temperature ceramic composites have significant strengthening effect. With the increase of (BNNT-BNNP) content, the strengthening effect of the composite is more obvious. During the cooling phase of the composite prepared by spark plasma sintering, a large number of dislocations were formed in the Zr B2 phase due to the significant differences in the thermal expansion coefficients of the composition phases, and the dislocations were mainly composed of fixed dislocations. These fixed dislocations will hinder the movement of the movable dislocations and increase the resistance of the plastic deformation of the composite material, resulting in obvious deformation strengthening effect of the composite material.