An electron microscopy appraisal of tensile fracture in metallic glasses
An electron microscopy appraisal of tensile fracture in metallic glasses
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DOI：
10.1016/j.actamat.2007.12.029
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发表时间：
2008-05
期刊：
影响因子：
9.4
通讯作者：
D. Matthews;V. Ocelík;P. Bronsveld;J. Hosson
中科院分区：
文献类型：
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作者：
D. Matthews;V. Ocelík;P. Bronsveld;J. Hosson
选择三种玻璃形成合金组合物用于带材生产和随后的电子显微镜研究。原位拉伸试验与透射电子显微镜（TEM），然后由非原位TEM和非原位扫描电子显微镜（SEM），允许在拉伸断裂的金属玻璃的变形过程进行分析。原位剪切带的传播被发现是跳跃式的，跳跃位置与二次剪切带的形成相关。本文还讨论了原位加热对结构弛豫的影响。观察到断裂表面附近的纳米晶化，然而，在同一样品中也没有结晶的报道，并讨论了其原因。TEM和SEM观察证实了带状物断裂表面上或附近存在液体状层。通过断口上的脉状结构和脉状密度表征了类液层的形成，并讨论了其与剪切位移δ的关系。一个简单的模型适用于剪切带的玻璃化转变和熔化温度过程中的温度上升，这是用来解释各种断裂面，这是宏观上相同的拉伸试验的金属玻璃连同功能，表现出局部熔化。
Three glass-forming alloy compositions were chosen for ribbon production and subsequent electron microscopy studies. In situ tensile testing with transmission electron microscopy (TEM), followed by ex situ TEM and ex situ scanning electron microscopy (SEM), allowed the deformation processes in tensile fracture of metallic glasses to be analysed. In situ shear band propagation was found to be jump-like, with the jump sites correlating with the formation of secondary shear bands. The effect of structural relaxation by in situ heating is also discussed. Nanocrystallization near the fracture surface was observed; however, no crystallization was also reported in the same sample and the reasons for this are discussed. Both the TEM and the SEM observations confirmed the presence of a liquid-like layer on or near the fracture surface of the ribbons. The formation of a liquid-like layer was characterized by the vein geometries and vein densities on the fracture surfaces and its dependence on shear displacement, δ, is discussed. A simple model is adapted to relate the temperature rise during shear banding to the glass transition and melting temperatures and this is used to explain the variety of fracture surfaces which are developed for macroscopically identical tensile testing of metallic glasses together with features which exhibit local melting.