The Influence of Directly Plating Time on the Structure of Electroless Nickel on AZ91

In this paper, the influence of deposition time on the surface morphology, composition, structure, grain size and hardness of electroless nickel plated directly in neutral pH bath on AZ91 magnesium alloy are discussed by using SEM, EDS, XRD and microhardness test machine measurements. The results show that with the increasement of the plating time, the surface tends to be smooth, dense, and complete. The coating is composed of Ni and P and the content of P increases with the increasing the plating time. Furthermore, the XRD peaks for the coatings shift to the right and broaden gradually with prolonged plating time, which indicates that the interplanar spacing of the crystal and the grain size are simultaneously decreased. At the same time, the microhardness of the samples is also increased with increasing plating time.