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A nanotwinned surface is formed on a titanium alloy under nanoindentations. Prior to nanoindentation, blocks of a ternary titanium alloy are machined by chemical mechanical polishing. The surface roughness Ra and peak-to-valley values are 1.135 nm and 8.82 nm, respectively. The hardness in the indented surface is greatly increased, indicated from the load-displacement curves compared to the polished surfaces. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is uniformly generated by nanoindentations at room temperature, which is different from previous findings, in which high temperature, high pressure, or chemical reagents are usually used. The nanotwinned surface is produced by pure mechanical stress, neither material removal nor addition.

In this study, nanotwinned surface is fabricated on a Nickel alloy by means of a developed diamond panel with tips array. The diamond panel has an area of 10×10 mm2, and is grown using microwave chemical vapor deposition. The diamond tips are submicron in radius and formed on a silicon substrate with an array full of uniformed inverted pyramid pits. The nanotwinned surface is produced under the pressure of 1 MPa exerted by the diamond panel with tips array. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is generated by indention of diamond panel at room temperature using mechanical force, neither material removal nor chemical reagents. This is different from previous reports, in which high temperature, high pressure, chemical reagents or vacuum conditions are employed usually.

In this study, eight nanotwinned cadmium telluride (CdTe or CZ) models were employed to investigate the synergistic and strengthening mechanism of twin boundaries under nanoindentations, using molecular dynamics (MD) simulations. Twin thickness between adjacent boundaries of 16 nm exhibited the maximum hardness during unloading conditions, among eight MD models with twin thickness varied from 4 to 23 nm. The maximum hardness was formed by the synergistic and strengthening effect induced by the stress fields between upper and lower twin boundaries under nanoindentations. When the twin thickness was less than 16 nm, the hardness increased with increasing twin thickness. Whereas, when the twin thickness was more than 16 nm, the hardness decreased with increasing twin thickness.