Tensile behavior of Al1-xMox crystalline and amorphous thin films
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- Tensile behavior of Al1-xMox crystalline and amorphous thin films
- Gianola, D. S.; Lee, Zonghoon; Ophus, C.; Luber, E. J.; Mitlin, D.; Dahmen, U.; Hemker, K. J.; Radmilovic, V. R.
- Alloy compositions; Amorphous metals; Amorphous phase; Amorphous thin films; Body-centered cubic; Composition ranges; Cosputtering; Elastic properties; Face-centered cubic; Free-standing thin films; Mechanical behavior; MEMS/NEMS; Micro-structural; Mo content; Nanocrystalline metal; Plastic property; Poisson's ratio; Rule of mixture; Single-step; Solute strengthening; Tensile behaviors; Two-phase region; Ultra-fine-grained
- Issue Date
- PERGAMON-ELSEVIER SCIENCE LTD
- ACTA MATERIALIA, v.61, no.5, pp.1432 - 1443
- The exceptional strength and distinct deformation physics exhibited by pure ultrafine-grained and nanocrystalline metals in comparison to their microcrystalline counterparts have been ascribed to the dominant influence of grain boundaries in accommodating plastic flow. Such grain-boundary-mediated mechanisms can be augmented by additional strengthening in nanocrystalline alloys via solute and precipitate interactions with dislocations, although its potency is a function of the changes in the elastic properties of the alloyed material. In this study, we investigate the elastic and plastic properties of Al1-xMox alloys (0 <= x <= 0.32) by tensile testing of sputter-deposited freestanding thin films. Isotropic elastic constants and strength are measured over the composition range for which three microstructural regimes are identified, including solid solutions, face-centered cubic and amorphous phase mixtures and body-centered cubic (bcc)/amorphous mixtures. Whereas the bulk modulus is measured to follow the rule of mixtures over the Mo composition range, the Young's and shear moduli do not. Poisson's ratio is non-monotonic with increasing Mo content, showing a discontinuous change at the onset of the bcc/amorphous two-phase region. The strengthening measured in alloyed thin films can be adequately predicted in the solid solution regime only by combining solute strengthening with a grain boundary pinning model. The single-step co-sputtering procedure presented here results in diversity of alloy compositions and microstructures, offering a promising avenue for tailoring the mechanical behavior of thin films.
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