Grain size and sample size interact to determine strength in a soft metal

• Published in: Philosophical magazine (Abingdon, England) Vol. 88; no. 25; pp. 3043 - 3050
• Main Authors: Ehrler, B., Hou, X.D., Zhu, T.T., P'ng, K.M.Y., Walker, C.J., Bushby, A.J., Dunstan, D.J.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 01.09.2008; Taylor & Francis
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deformation and plasticity (including yield, ductility, and superplasticity); Deformation, plasticity, and creep; Exact sciences and technology; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; metal foil; microband tests; nickel; Physics; plasticity; size effect; strain measurement; Treatment of materials and its effects on microstructure and properties; Grain size; Strengthening; High strain; Work hardening; Symmetry property; Plastic flow; Plastic deformation; Finite strain; Stress-strain relations; Hardening; Crystallites; Yield point; Size effect; Strain measurement; Nickel; Property structure relationship; Nanotechnology; Flow stress; Stress measurement; Physical Sciences
• ISSN: 1478-6435; 1478-6443; 1478-6433
• DOI: 10.1080/14786430802392548

Understanding the strengthening of small-scale materials and structures is one of the key issues in nanotechnology. Many theories exist, each addressing a small domain of experimentally observed size effects and invoking different mechanisms. Measurements of the stress-strain relationship of nickel foils in flexure by the load-unload method provide strikingly accurate data from the elastic region through the yield point and to high plastic strain. The data show that the effects on the rate of work-hardening due to crystallite size and sample size interact, whereas in existing theories they should be independent. Existing theories cannot be complete. The symmetry of the dependence of flow stress on grain size and structure size suggests that strengthening effects are due to a finite strained volume, however this is delimited.