灰口铸铁中石墨及其与基体界面的微力学行为

Graphite and It-Matrix Interface Micromechanical Behaviours in Grey Iron

用扫描电镜原位观察技术，发现灰口铸铁拉伸裂纹并非先在石墨尖端基体中，而是先在呈有利取向的石墨—基体（Ｇ—ｍ）界面（含亚界面石墨）中萌生．提出不是石墨微缺口应力集中，而是界面弱结合及近界面Ｇ、ｍ的不协调形变内应力集中导致Ｇ—ｍ界面断裂．这种断裂在拉伸早期就已开始，并随拉伸而逐步增加，既有沿Ｇ基面的正断，也有沿Ｇ基面的斜断和非基面的强键断裂．这样裂开后Ｇ成为如其形状的裂隙，引起微缺口应力集中，影响其近邻基体的形变与断裂等微力学行为．

By using the in situ observation technique under SEM it was found that under tensile loading, in grey cast iron, a crack did not initiate first at the matrix ahead of graphite tip but at the graphite-matrix interface (including the graphite subsurface, similarly here after). It is proposed that the weak interface and the internal stress concentration resulting from the incompatible deformation between G and M adjacent to the interface rather than the plate graphite micro-notch stress concentration lead to the G-M interfacial cracking. This cracking starts from the early tensile loading stage and increases steadily with the advance of the loading process. There are not only the normal but also the incline fracturing along the graphite basal plane, and the strong band basal fracturing. After being cracked, G becomes cradks shaped like themselves which lead to a micro-notch stress concentration and affect the micro-mechanical behaviours of deformation and fracture of adjacent matrix.