Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Science. 2020 Aug 7;369(6504):689-694. doi: 10.1126/science.aba9490.
Steels for sharp edges or tools typically have martensitic microstructures, high carbide contents, and various coatings to exhibit high hardness and wear resistance. Yet they become practically unusable upon cutting much softer materials such as human hair, cheese, or potatoes. Despite this being an everyday observation, the underlying physical micromechanisms are poorly understood because of the structural complexity of the interacting materials and the complex boundary conditions of their co-deformation. To unravel this complexity, we carried out interrupted tests and in situ electron microscopy cutting experiments with two micromechanical testing setups. We investigated the findings analytically and numerically, revealing that the spatial variation of lath martensite structure plays the key role leading to a mixed-mode II-III cracking phenomenon before appreciable wear.
用于锋利边缘或工具的钢材通常具有马氏体微观结构、高碳化物含量和各种涂层，以表现出高硬度和耐磨性。然而，当它们切割更软的材料，如人类的头发、奶酪或土豆时，它们就变得几乎无法使用了。尽管这是一个日常观察，但由于相互作用材料的结构复杂性和它们共同变形的复杂边界条件，基础物理微观机制仍未得到很好的理解。为了解开这种复杂性，我们使用两种微机械测试设备进行了中断测试和原位电子显微镜切割实验。我们对结果进行了分析和数值模拟，揭示了板条马氏体结构的空间变化在明显磨损之前起着关键作用，导致了混合模式 II-III 裂纹现象。
