Planar Defect Nucleation and Annihilation Mechanisms in Nanocontact Plasticity of Metal Surfaces

Jorge Alcalá, Roger Dalmau, Oliver Franke, Monika Biener, Juergen Biener, and Andrea Hodge

Phys. Rev. Lett. 109, 075502 – Published 16 August 2012

Abstract

The incipient contact plasticity of metallic surfaces involves nucleation of crystalline defects. The present molecular dynamics simulations and nanoindentation experiments demonstrate that the current notion of nanocontact plasticity in fcc metals does not apply to high-strength bcc metals. We show that nanocontact plasticity in Ta—a model bcc metal—is triggered by thermal and loading-rate dependent (dynamic) nucleation of planar defects such as twins and unique ${011}$ stacking fault bands. Nucleation of different planar defects depending on surface orientation leads to distinct signatures (pop ins) in the nanoindentation curves. Nanoscale plasticity is then ruled by an outstanding dynamical mechanism governing twin annihilation and subsequent emission of linear defects (full dislocations). While this investigation concerns Ta crystals, the present are landmark findings for other model bcc metals.

Received 30 January 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.075502

Authors & Affiliations

Jorge Alcalá¹, Roger Dalmau¹, Oliver Franke², Monika Biener³, Juergen Biener³, and Andrea Hodge²

¹Department of Materials Science and Metallurgical Engineering, GRICCA, EUETIB and ETSEIB, Universitat Politècnica de Catalunya, C. Comte d’Urgell 187, 08036 Barcelona, Spain
²Department of Aerospace and Mechanical Engineering, University of Southern California, 3650 McClintock Avenue, Los Angeles, California 90089, USA
³Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA