Date of Award
Santa Clara : Santa Clara University, 2018.
Master of Science (MS)
With the use of molecular dynamics simulations, the nanoscale contact between two aluminum substrates at room temperature is studied. The so-called jump-to-contact (JC) phenomenon between (111) surfaces is observed to occur for interfacial distances below 5.8 ± 0.05 Å. This critical distance is approximately equal to 2.5 times the interplanar spacing of (111) planes in a perfect aluminum crystal at 300 K. The critical distance for JC is shown to be higher at higher contact temperatures because of the higher amplitude of atomic vibrations. The effect of employed interatomic potential on the critical distance is also discussed.
The critical distance for JC is shown to be independent of crystallographic misorientation between substrates. However, the final distribution of crystallographic defects at the bonded interface is controlled by the misorientation angle. Three ranges of misorientation angles of (I) 0°<𝜃<21.79°, (II) 21.79°<𝜃<38.21°, and (III) 38.21°<𝜃<60° are found to be important with regard to the distribution of crystallographic defects. The initial gap size between substrates is shown to affect the density of crystallographic defects in ranges (I) and (III) of misorientation, where dislocations and point defects exist at the interface. On the contrary, the final density of defects in range (II) is independent of initial separation between surfaces since the whole interface is a typical planar defect.
Khajehvand, Milad, "Crystal Misorietation and Defect Generation during Contact between Two Aluminum Substrates" (2018). Mechanical Engineering Master's Theses. 24.