Strain rate sensitivity of nanolayered Cu/X (X=Cr, Zr) micropillars: Effects of heterophase interface/twin boundary

Manipulation of internal features, e.g., layer/twin interfaces, is standard practice in engineering structural materials to tailor their properties. In the present work, we fabricated nanotwinned (NT)- and nanocrystalline (NC)–Cu/X (X=Cr, Zr) nanolayered micropillars (NLs) with equal layer thickness...

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Bibliographic Details
Published in:	Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2014-08, Vol.612, p.28-40
Main Authors:	Zhang, J.Y., Wang, Y.Q., Wu, K., Zhang, P., Liu, G., Zhang, G.J., Sun, J.
Format:	Article
Language:	eng
Subjects:	Applied sciences BOUNDARIES Condensed matter: structure, mechanical and thermal properties Copper Defects and impurities in crystals microstructure Density Evolution Exact sciences and technology Grain and twin boundaries Interface INTERFACES Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology Metals. Metallurgy Microstructure MICROSTRUCTURES Nanolayered micropillars Nanostructure Physics Size effect STRAIN STRAIN RATE SENSITIVITY Structural materials Structure and morphology thickness Structure of solids and liquids crystallography Surfaces and interfaces thin films and whiskers (structure and nonelectronic properties) Thin film structure and morphology TWIN BOUNDARIES Twin boundary TWINNING MECHANISMS
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Summary:	Manipulation of internal features, e.g., layer/twin interfaces, is standard practice in engineering structural materials to tailor their properties. In the present work, we fabricated nanotwinned (NT)- and nanocrystalline (NC)–Cu/X (X=Cr, Zr) nanolayered micropillars (NLs) with equal layer thickness (h) spanning from 5 to 125nm. The microcompression methodology was employed to investigate the layer/twin interfaces effects on plastic characteristics of nanolayered materials at different strain rates. Experimental results clearly unveil that the Cu/X NTNLs exhibit a significant increase in strength and in strain rate sensitivity (SRS) by introducing nanotwins, in comparison with the Cu/X NCNLs. The non-monotonic evolution of SRS with h observed in the Cu/X NTNLs is explained by a competition between the monotonically increased interfaces density and the decreased twin boundaries density with reduction in feature size h. Unlike the monotonically enhanced SRS of Cu/X NCNLs, the SRS of Cu/X NTNLs first decreases and subsequently increases with reducing h. A phenomenological model is proposed to rationalize these experimental findings and highlight the microstructural feature size effects on the rate-limiting processes of metallic materials.
ISSN:	0921-5093 1873-4936