STRUCTURE AND TRANSFORMATION BEHAVIOR OF NANOCRYSTALLINE NICKEL-PHOSPHORUS ALLOYS

By electroless deposition coatings of nickel-phosphorus alloys up to a bout 100 mu m thick can be deposited onto metallic and nonmetallic sub strates. At phosphorus contents between 2 and 8 mass% the coatings exh ibit a nanocrystalline structure. The process of the deposition of suc h coatings is described. The microstructure of the coatings is analyse d by using X-ray diffraction, transmission electron microscopy and fie ld ion microscopy. As a result, the grain size of the coatings varies between 2 and 10 nm depending on the phosphorus content. When heated a t a rate of 5 K/min, excessive grain growth occurs at a temperature be tween 350 and 400 degrees C, when the equilibrium phase Ni3P is formed . In the as-deposited state the nanosized supersaturated nickel crysta ls seem to be surrounded by an amorphous phosphorus-rich phase. At 150 degrees C a relaxation and an increase in the phosphorus content of t he amorphous phase can be observed.