Structure and mechanical properties of Cu-X (X = Nb,Cr,Ni) nanolayered composites

Sputtered Cu/Cr and Cu/Nb multilayers have polycrystalline microstructures with nanometer scale grain sizes, while Cu/Ni multilayers evaporated on single crystal Cu or NaCl were single crystalline. The hardness of the multilayers for layer thicknesses (h) > 50 nm is explained by Hall-Petch model with grain boundaries and interfaces as barriers. At h < 50 nm, a deviation from the Hall-Petch behavior is observed for all three composites. In this regime, plastic flow is believed to occur by single dislocations gliding on closely spaced planes with flow stress proportional to (1/h)ln(h/b). High hardnesses in nanolayered composites result from a combination of increased yield strength and increased work hardening rate at low h.

[1]  W. Nix.  Elastic and plastic properties of thin films on substrates : nanoindentation techniques , 1997 .

[2]  Don M. Parkin,et al.  Mechanical Properties and Deformation Behavior of Materials Having Ultra-Fine Microstructures , 1993 .

[3]  Scott A. Barnett,et al.  Plastic and Elastic Properties of Compositionally Modulated Thin Films , 1994 .

[4]  A. Thompson.  Yielding in nickel as a function of grain or cell size , 1975 .

[5]  M. Nastasi,et al.  Observation of body centered cubic Cu in Cu/Nb nanolayered composites , 1997 .

[6]  M. Nastasi,et al.  Observations of Dislocations in Cu/Nb Nanolayer Composites After Deformation , 1997 .

[7]  W. A. Spitzig,et al.  Characterization of the strength and microstructure of heavily cold worked CuNb composites , 1987 .

[8]  S. Barnett,et al.  A Model of Superlattice Yield Stress and Hardness Enhancements , 1995 .

[9]  R. Armstrong,et al.  The plastic deformation of polycrystalline aggregates , 1962 .

[10]  G. Smith,et al.  Hall-petch dependence for ultrafine grain size electrodeposited chromium , 1985 .

[11]  M. Nastasi,et al.  The influence of microstructural scale on the combination of strength and electrical resistivity in copper based composites , 1995 .

[12]  T. Foecke,et al.  Deformation and fracture in microlaminates , 1996 .

[13]  K. Adachi,et al.  Strengthening Mechanism of Cold-Drawn Wire of in situ Cu-Cr Composite , 1997 .

[14]  J. Embury,et al.  On dislocation storage and the mechanical response of fine scale microstructures , 1994 .

[15]  J. Koehler.  Attempt to Design a Strong Solid , 1970 .

[16]  P. Anderson,et al.  Hall-Petch relations for multilayered materials , 1995 .