Twinning anisotropy of tantalum during nanoindentation

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:627

Article

Goel, Saurav¹  Beake, Ben^2,3  Chan, Chi-Wai¹  Faisal, Nadimul Haque⁴  Dunne, Nicholas¹ 

[1] Queens Univ, Sch Mech & Aerosp Engn, Belfast BT9 5AH, Antrim, North Ireland

[2] Micro Mat Ltd, Wrexham LL13 7YL, Wales

[3] Manchester Metropolitan Univ, Dalton Res Inst, Manchester M15 GD, Lancs, England

[4] Robert Gordon Univ, Sch Engn, Aberdeen AB10 7GJ, Scotland

关键词: MD simulation;    Nanoindentation;    Tantalum;    Anisotropy;   

DOI  :  10.1016/j.msea.2014.12.075

来源: Elsevier

【 摘 要 】

Unlike other BCC metals, the plastic deformation of nanocrystalline Tantalum (Ta) during compression is regulated by deformation twinning. Whether or not this twinning exhibits anisotropy was investigated through simulation of displacement-controlled nanoindentation test using molecular dynamics (MD) simulation. MD data was found to correlate well with the experimental data in terms of surface topography and hardness measurements. The mechanism of the transport of material was identified due to the formation and motion of prismatic dislocations loops (edge dislocations) belonging to the 1/2 < 111 > type and < 100 > type Burgers vector family. Further analysis of crystal defects using a fully automated dislocation extraction algorithm (DXA) illuminated formation and migration of twin boundaries on the (110) and (111) orientation but not on the (010) orientation and most importantly after retraction all the dislocations disappeared on the (110) orientation suggesting twinning to dominate dislocation nucleation in driving plasticity in tantalum. A significant finding was that the maximum shear stress (critical Tresca stress) in the deformation zone exceeded the theoretical shear strength of Ta (Shear modulus/2 pi similar to 10.03 GPa) on the (010) orientation but was lower than it on the (110) and the (111) orientations. In light of this, the conventional lore of assuming the maximum shear stress being 0.465 times the mean contact pressure was found to break down at atomic scale. (C) 2014 Elsevier B.V. All rights reserved.

【 授权许可】

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