Abstract
In this study, amorphous Ni-P films were deposited by electroless plating under different pH values. Their mechanical properties and deformation behavior were then investigated by instrumented nano-indentation. With increasing pH value of the plating solution from 3.75 to 6.0, the hardness and elastic modulus of the obtained Ni-P films increased from 6.1 GPa and 146 GPa to 8.2 GPa and 168 GPa respectively. From the load-indentation depth curve, the Ni-P films were found to yield at an indentation depth of 8 nm. By microstructural examination around the indented regions, early-stage plastic deformation of the amorphous Ni-P films was verified through the formation and extension of shear bands with a spacing of several tens of nanometers. Within the shear bands, flow dilatation-induced intense shear localization was expected and resulted in crystallization in the amorphous matrix. The critical shear stress and energy release rate required for the initiation of early-stage plastic yielding of the Ni-P films were calculated to be about 1.4 GPa and 3.0 J/m2 respectively, both of which increased with pH values.
Published Version
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