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Atomistic simulations of the formation and destruction of nanoindentation contacts in tungsten

: Hagelaar, J.H.A.; Bitzek, E.; Flipse, C.F.J.; Gumbsch, P.


Physical Review. B 73 (2006), Nr.045425, 14 S.
ISSN: 0163-1829
ISSN: 1098-0121
ISSN: 0556-2805
Fraunhofer IWM ()
Deformation and plasticity; yield; ductility; superplasticity; tribology and hardness; mechanical property of nanoscale material

This paper presents atomistic simulations of contact formation, indentation, sub sequent pulling, and contact failure between a tungsten tip and a tungsten substrate. Different combinations of [111] and [110] crystal directions parallel to the direction of indentation are investigated. The simulations are performed using a Finnis-Sinclair potential for tungsten and a displacement controlled, quasi static simulation scheme. The simulation setup and the tip geometry are inspired by low temperature scanning tunneling microscope indentationretraction experiments. In the case of identical crystalline orientation of tip and substrate, deformation during indentation and the early stages of retraction is carried exclusively by prismatic dislocation loops. When the so formed nanocontact between the tip and substrate gets smaller, the deformation mechanism changes to atomic rearrangements within the neck. For configurations with different crystallographic orientation of the tip and substrate, the deformation is mainly carried by local atomic rearrangements within the interface region. Failure of the contact always occurs at the interface. In all cases debris is leftover on the substrate. The simulation results are discussed in the framework of nanoindentation and contact failure. The importance of the atomistic structure of interfaces in nanoscale contact problems is highlighted.