Journal of Materials Research


Nanoindentation and incipient plasticity

E. B. Tadmora1 p1, R. Millera1 p2, R. Phillipsa1 c1 and M. Ortiza2

a1 Division of Engineering, Brown University, Providence, Rhode Island 02912

a2 Department of Aeronautics, California Institute of Technology, Pasadena, California 91125


This paper presents a large-scale atomic resolution simulation of nanoindentation into a thin aluminum film using the recently introduced quasicontinuum method. The purpose of the simulation is to study the initial stages of plastic deformation under the action of an indenter. Two different crystallographic orientations of the film and two different indenter geometries (a rectangular prism and a cylinder) are studied. We obtain both macroscopic load versus indentation depth curves, as well as microscopic quantities, such as the Peierls stress and density of geometrically necessary dislocations beneath the indenter. In addition, we obtain detailed information regarding the atomistic mechanisms responsible for the macroscopic curves. A strong dependence on geometry and orientation is observed. Two different microscopic mechanisms are observed to accommodate the applied loading: (i) nucleation and subsequent propagation into the bulk of edge dislocation dipoles and (ii) deformation twinning.

(Received August 19 1998)

(Accepted March 01 1999)


c1 Address all correspondence to this author. e-mail:

p1 Present address: Faculty of Mechanical Engineering, Technion–Israel Institute of Technology, 32000 Haifa, Israel.

p2 Present address: Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, Canada.