Crystallization of Ni–P Fabricated by Electroless Deposition: Microscopic Mechanism

Abstract

ABSTRACTWe investigate the crystallization of amorphous Ni–P with near-eutectic composition, fabricated by electroless plating as a 10 µm thick continuous layer. Aiming to understand phase transformations that occur upon heating and, in particular, the microscopic mechanism of crystallization, we combine a variety of complimentary characterization techniques. DSC (differential scanning calorimetry) during isothermal heating reveals the crystallization kinetics. Conventional-, high-resolution-, and analytical TEM (transmission electron microscopy) and TEM-based electron diffraction provide high-spatial-resolution information on phase nucleation and spatial distribution of atom species, particularly the crystallography of the nucleating crystalline phases (Ni3P and Ni) and the spatial distribution of phosphorus in the partially and completely crystallized alloy. Our results indicate that crystallization proceeds by homogeneous nucleation of Ni3P grains. Internally, these exhibit a microstructure of radially oriented subgrains containing Ni nano-platelets in a specific crystallographic OR (orientation relationship) with Ni3P. However, the preferred Ni–Ni3P OR differs from those reported in the literature for similar material. Combining our observation on the structure and microstructure of partially and completely crystallized Ni–P with the observed crystallization kinetics provides a deeper understanding of the microscopic mechanism of crystallization.