October 4-9, 2015
By using microcompression methodology, deformation of nanolayered crystal/crystal (C/C) Cu/Zr and Cu/ Cr, and crystal/amorphous (C/A) Cu/CuZr micropillars was systematically investigated within wide ranges of intrinsic layer thickness (5 – 150 nm) and extrinsic sample diameter (300 – 1500 nm). The intrinsic size effect, extrinsic size effect and their interplay were respectively revealed. Competition between the intrinsic and extrinsic size effects leads to a common experimental observation of a critical layer thickness of about 20 nm, above which the deformation is predominantly intrinsic-size-related and insensitive to sample size, while below which the two size effects are comparable. The underlying deformation mechanisms are proposed to transform from bulk-like to small-volume materials behavior. Deformation mode is correspondingly transited from homogeneous extrusion/barreling to inhomogeneous shear banding, and the two competing modes coexist in the layer thickness range from about 50 to 20 nm. Besides these generalities, specific deformation features of the C/C and C/A micropillars are respectively discussed. In particular, deformation-induced devitrification in the amorphous layers promotes an extraordinary plasticity in the C/A micropillars, which provides a viable route to enhance the controllability of plastic deformation in metallic glassy composites. A deformation mode map is further developed to clearly elucidate the coupling intrinsic and extrinsic size effects on the deformation mode of nanolayered micropillars.
Gang Liu, Jin Zhang, and Jun Sun, "Length-scale dependent deformation behavior of nanolayered Cu-based micropillars" in "Nanomechanical Testing in Materials Research and Development V", Dr. Marc Legros, CEMES-CNRS, France Eds, ECI Symposium Series, (2015). http://dc.engconfintl.org/nanomechtest_v/50