Microstructure and morphology of electrodeposited Ni–P alloys treated by high energy surface mechanical attrition

Fully amorphous Ni–P layer electrodeposited onto a Cu plate was subjected to severe plastic deformation using surface mechanical attrition treatment in a high energy SPEX 8000 shaker mill. Two series of experiments using different milling conditions (series I: 20 6.35-mm balls; series II: 100 1.59-mm balls) were carried out to explore the mechanism of the process and to investigate the structure of the developed coatings. The evolution of the microstructure and mechanical properties of the Ni–P layer after the deformation process was studied by x-ray diffraction, scanning electronmicroscopy and hardness measurements. We demonstrate that the different mechanical treatments controllably influence the mechanical behavior of the Ni–P metallic glass coating. When the vial of the mill is loaded with larger balls, deformation-induced Ni3P compound particles form in the amorphous matrix resulting in a hard (HV = 17 GPa) but non-uniform coating. In the case of milling with many small balls, the increase in the surface hardness is considerably lower (7 GPa) as a consequence of reduced impact energy.