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Plastic deformation of nanocrystalline copper-antimony alloys Rahul K. Rajgarhia, Douglas E. Spearot,a) and Ashok Saxena Department of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (Received 4 August 2009; accepted 3 December 2009)

Molecular dynamics simulations are used to evaluate the influence of Sb dopant atoms at the grain boundaries on plastic deformation of nanocrystalline Cu. Deformation is conducted under uniaxial tensile loading, and Sb atoms are incorporated as substitutional defects at the grain boundaries. The presence of randomly dispersed Sb atoms at the grain boundaries does not appreciably influence the mechanisms associated with dislocation nucleation in nanocrystalline Cu; grain boundary ledges and triple junctions still dominate as partial dislocation sources. However, the magnitude of the tensile stress associated with the partial dislocation nucleation event does increase with increasing Sb concentration and also with increasing grain size. The flow stress of nanocrystalline Cu increases with increasing Sb concentration up to 1.0 at.% Sb, with a maximum observed at a grain size of 15 nm for all Sb concentrations (0.0–2.0 at.% Sb). I. INTRODUCTION

Metallic nanocrystalline materials exhibit increased strength, wear resistance, and radiation damage resistance in comparison to coarse-grained metallic materials.1 The unique properties of nanocrystalline materials are attributed to the high volume fraction of grain boundaries and thus a significant percentage of atoms being located at or near interfacial regions.2,3 Unfortunately, it is also well known that nanocrystalline materials are prone to grain growth at stress and temperature levels well below that of their microcrystalline counterparts, raising questions about their use during long-term service as structural materials. For example, experimental results have shown that nanocrystalline Cu undergoes microstructural coarsening at room temperature,4–6 resulting in a loss of the properties attributed to the fine grain size. The key to realizing the full potential of metallic nanocrystalline materials lies in the development of methods to stabilize their microstructure and thus prevent degradation of their properties when placed in service. Molecular dynamics (MD) simulations7 and theoretical results8 have proposed that the microstructure of nanocrystalline materials can be stabilized by adding dopants at the grain boundaries. For example, in recent experimental work, it was shown that the recrystallization temperature a)

Address all correspondence to this author. e-mail: [email protected] This paper was selected as an Outstanding Symposium Paper for the 2008 MRS Fall Meeting, Symposium W Proceedings, Vol. 1130E. DOI: 10.1557/JMR.2010.0072 J. Mater. Res., Vol. 25, No. 3, Mar 2010

of nanocrystalline Cu can be increased from 150  C to approximately 400  C by adding 0.2 or 0.5 at.% antimony (Sb) that segregates to the grain boundaries.9 Although dopants can be used to improve microstructural stability, there is li