Plastic yielding in nanocrystalline Pd-Au alloys mimics universal behavior of metallic glasses
Authors:
A. Leibner,
C. Braun,
J. Heppe,
M. Grewer,
R. Birringer
Abstract:
We studied solid solution effects on the mechanical properties of nanocrystalline (NC) $\mathrm{Pd}_{\mathrm{100-x}} \mathrm{Au}_{\mathrm{x}}$ alloys ($0 \leq \mathrm{x} < 50 \mathrm{at.\%}$) at the low end of the nanoscale. Concentration has been used as control parameter to tune material properties (elastic moduli, Burgers vector, stacking fault energies) at basically unaltered microstructure (g…
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We studied solid solution effects on the mechanical properties of nanocrystalline (NC) $\mathrm{Pd}_{\mathrm{100-x}} \mathrm{Au}_{\mathrm{x}}$ alloys ($0 \leq \mathrm{x} < 50 \mathrm{at.\%}$) at the low end of the nanoscale. Concentration has been used as control parameter to tune material properties (elastic moduli, Burgers vector, stacking fault energies) at basically unaltered microstructure (grain size $D\approx 10\mathrm{ nm}$). In stark contrast to coarse grained fcc alloys, we observe solid solution softening for increasing Au-content. The available predictions from models and theories taking explicitly into account the effect of the nanoscale microstructure on the concentration-dependent shear strength have been disproved without exception. As a consequence, it is implied that dislocation activity contributes only marginally to strength. In fact, we find a linear correlation between shear strength and shear modulus which quantitatively agrees with the universal behavior of metallic glasses discovered by Johnson and Samwer [W.L. Johnson and K. Samwer, PRL 95, 195501 (2005)].
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Submitted 7 January, 2016; v1 submitted 9 December, 2014;
originally announced December 2014.