Microstructure and properties of electroformed nickel under different waveform conditions

In order to prepare electroformed nickel with excellent properties, the effect of different waveforms on microstructure and mechanical properties was investigated by optical microscopy (OM), X-ray diffraction (XRD) and tensile test, respectively. The results show that the samples are composed of micron columnar grains with high-density nanoscale coherent twin boundaries which are parallel to the growth plane. The tensile strength and elongation display opposite tendency with the increase in current density when direct current (DC) electroforming was applied. However, under the condition of pulse current (unidirectional, bidirectional) electroforming, the change regulation of tensile strength and elongation is close while cathode (peak, positive peak) current density increases. XRD results show that electroformed nickel layers with high purity are all fcc crystal configuration under different conditions of the current waveform. The nickel layers formed under bidirectional pulse current behave superior global performance with tensile strength of 692.0 MPa and elongation of 27.6 %.