Abstract
In this work, Al-Cr-N ceramic films deformed by nanoindentation were peeled off from silicon substrates and their atomic-scale microstructures underneath the indenter were investigated by high resolution transmission electron microscope (HR-TEM). Dislocations were formed underneath the indenter and they accumulated along nano-grain boundaries. The accumulative dislocations triggered the crack initiation along grain boundaries, and further resulted in the crack propagation. Dislocations were also observed in nano-grains on the lateral contact area. A model was proposed to describe the variation of microstructures under nanoindentation.
Highlights
Thin films are generally used as engineering materials based on their superb mechanical properties.[1,2,3,4] For such kinds of materials, numerous works focus on how to obtain good mechanical properties by optimizing experimental parameters, such as bias voltage and gas flow ratio.[5,6,7,8,9] the microstructure of thin films determines their mechanical properties
Al-Cr-N ceramic films deformed by nanoindentation were peeled off from silicon substrates and their atomic-scale microstructures underneath the indenter were investigated by high resolution transmission electron microscope (HR-TEM)
How does the microstructure impede the indentation process? How does the microstructure vary after indentation? Many publications have been dedicated to these issues, trying to unveil what has happened on the microstructure underneath the indenter
Summary
Thin films are generally used as engineering materials based on their superb mechanical properties.[1,2,3,4] For such kinds of materials, numerous works focus on how to obtain good mechanical properties by optimizing experimental parameters, such as bias voltage and gas flow ratio.[5,6,7,8,9] the microstructure of thin films determines their mechanical properties. Nanoindentation technique is frequently used to characterize the mechanical properties of thin films, such as hardness, reduced modulus and fracture toughness.[10,11,12] During an indentation process, the indenter tip is pressed into thin films and the data of load and displacement are collected synchronously These data are directly affected by the microstructure underneath the indenter. The other kind is the in-situ nanoindentation inside an electron microscopy Both of these methods focus on the zone underneath an indenter from the perspective of cross section. A fully understanding of the atomic scale microstructures underneath an indenter, not just the cross-section part, is needed This will contribute to unveiling the mechanism of the interaction between microstructures and the indenter during a complicated indentation process. Based on the atomic-scale experimental observations, a model was proposed to describe the variations of microstructures under an indenter
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