A new criterion for elasto-plastic transition in nanomaterials: Application to size and composite effects on Cu–Nb nanocomposite wires

• Published in: Acta materialia 2009-06, Vol.57 (11), p.3157-3169
• Main Authors: Thilly, Ludovic, Petegem, Steven Van, Renault, Pierre-Olivier, Lecouturier, Florence, Vidal, Vanessa, Schmitt, Bernd, Swygenhoven, Helena Van
• Format: Article
• Language: English
• Subjects: Applied sciences; Bauschinger effect; Exact sciences and technology; Line broadening; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Nanocomposite; Plastic deformation; X-ray diffraction
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2009.03.021

Nanocomposite wires composed of a multi-scale Cu matrix embedding Nb nanotubes are cyclically deformed in tension under synchrotron radiation in order to follow the X-ray peak profiles (position and width) during mechanical testing. The evolution of elastic strains vs. applied stress suggests the presence of phase-specific elasto-plastic regimes. The nature of the elasto-plastic transition is uncovered by the “tangent modulus” analysis and correlated to the microstructure of the Cu channels and the Nb nanotubes. Finally, a new criterion for the determination of the macroyield stress is given as the stress to which the macroscopic work hardening, θ a = d σ a/d ε 0, becomes smaller than one third of the macroscopic elastic modulus.