The mechanical behavior of incoherent Cu/Zr multilayers was studied in uniaxial compression experiments using micropillars with individual layer thicknesses (h) ranging from 5 to 100 nm. The deformation behavior of these micropillars are size dependent, transiting from dislocation dominated symmetrical slip at large h to shear localization induced by asymmetric slip and grain boundary mediated deformation at small h. During compression studies the multilayer micropillars exhibit a transition from strain hardening to shear softening at small h, and work softening at greater h. A maximum strain hardening rate is observed at a critical h of 20 nm, which was explained in terms of a transition from dislocation interactions to cross-slip of dislocations. The mechanical strength of the micropillars is also dependent on h, which was quantitatively analyzed using the confined layer slip model. In addition, the influence of pillar diameter on the mechanical behavior is also investigated. The effect of extrinsic size on the deformation mechanisms is discussed with respect to the intrinsic size effect with variation in h.
Bibliographical noteFunding Information:
This work was supported by the 973 Program of China (Grant No. 2010CB631003), the 111 Project of China (B06025) and the National Natural Science Foundation of China (50971097). G.L. thanks the Fundamental Research Funds for the Central Universities for support and J.Y.Z. thanks the China Scholarship Council for financial support. X.Z. acknowledges financial support by the NSF-DMR Metallic Materials and Nanostructures Program, under Grant No. 0644835.
- Nanolayered micropillar
- Plastic deformation
- Strain hardening
- Strain softening