Microscopic properties of nanocrystal Aluminum thin film have been simulated using the quasicontinuum method in order to study the surface defect influence in nanoindentation. Various distances between the surface defect and indenter have been taken into account. The results show that as the distance between the pit and indenter increases, the nanohardness increases in a wave pattern associated with a cycle of three atoms, which is closely related to the crystal structure of periodic atoms arrangement on {111} atomic close-packed planes of face-centered cubic metal; when the adjacent distance between the pit and indenter is more than 16 atomic spacing, there is almost no effect on nanohardness. In addition, the theoretical formula for the necessary load for elastic-to-plastic transition of Al film has been modified with the initial surface defect size, which may contribute to the investigation of material property with surface defects.
We carried out various distances cases between the surface defect and indenter, in order to study the surface defect influence in nanoindentation. Actually, it is extremely difficult to guarantee no parameters changing only except the distance during experiments. So, there is no exactly same experiment.
However, a few investigations have showed the periodicity in some micro parameters [1]. Additionally, the generalized planar fault (GPF) curve in FCC metal has been already demonstrated to be periodic [2]. These above can be strong evidences to the result in present paper that the distance influence between the pit and the indenter on nanohardness fits a wave pattern is due to periodic the stacking sequence of (111) planes.
[1]Yu, W. S., Shen, S. P., Materials Science and Engineering A. 526(2009) 211-218
[2]H. VAN. SWYGENHOVEN, P. M. DERLET AND A. G.. FRØSETH, NATURE MATERIALS. Volume: 3 Issue: 6 Pages: 399-403
Our work is aimed to investigate whether there is the physical principle or not. So, multiscale simulation really help us a lot to control various constraint conditions. But we will also make further study to find more evidences in real experiments.
Thanks again.
