Abstract
To clarify the influence mechanism of strain rate effect on deformation characteristics of aluminum nitride (AlN) ceramics, some varied-velocity nanoscratching tests were carried out using a Berkovich indenter in this paper. The deformation characteristics of the scratched grooves were observed using the scanning electron microscope. The experimental results showed higher scratch speed would lead to shallower penetration depth, fewer cracks, and indenter fewer slipping, which was more conducive to the plastic deformation of AlN ceramics. Considering the strain rate effect and the elastic recovery of material, a model for predicting the Berkovich indenter penetration depth under edge-forward mode was established. The prediction results were consistent with the experimental data, and the error was less than 5%, indicating that the model is effective. Based on the Boussinesq field, the Cerruti field, and the Sliding bubble field, a strain rate dependent scratch stress field model was established. The stress field revealed higher scratch speed may significantly reduce the maximum principal stress in the stress field under the indenter, which is the fundamental reason for reducing the crack damage and promoting the plastic deformation. The above study can provide theoretical guidance for reducing the processing damage of AlN ceramics.
Highlights
It is well known that aluminum nitride (AlN) ceramics have many excellent properties such as better thermal conductivity, reliable electrical insulation, nontoxicity, and thermal expansion coefficient matching with silicon [1,2,3]
We systematically studied the effect of strain rate on the deformation characteristics for AlN ceramic materials
It indicates that the slippage of the indenter has a great correlation with the cracks, and the material removal includes more than plastic deformation, but5 of brittle fracture as well
Summary
It is well known that aluminum nitride (AlN) ceramics have many excellent properties such as better thermal conductivity, reliable electrical insulation, nontoxicity, and thermal expansion coefficient matching with silicon [1,2,3]. Hard abrasive machining is the most traditional and important processing method for AlN ceramic substrates, such as grinding [6] and lapping [7]. AlN ceramics belong to the hard and brittle materials, with high hardness and high brittleness. These traits often lead to a series of surface/subsurface damages during abrasive machining such as severe surface defects, brittle cracks, and residual stresses [8,9]. The processing damages of the AlN ceramics substrate will greatly affect the performance of semiconductor devices and seriously shorten the service life of devices [10]. To improve the strength and reliability of AlN ceramics substrates in semiconductor devices, the surface/subsurface damage caused by abrasive machining must be controlled and minimized
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