Crystallization micro-mechanism of near-eutectic amorphous Ni–P

Complementary characterization techniques are applied to understand the crystallization micro-mechanism of near-eutectic amorphous Ni–P prepared by ELD (electroless deposition). DSC (differential scanning calorimetry) reveals the isothermal crystallization kinetics. XPS (X-ray photoelectron spectrometry) provides core-level electronic signatures of Ni and phosphorus, which reflect the evolution of SRO (short-range order) during crystallization. TEM (transmission electron microscopy) provides high-spatial-resolution information on phase nucleation and spatial distribution of atom species, particularly the crystallography of the nucleating Ni3P and Ni. Generally, the microstructure of crystallizing phases resembles what would be expected for solidification of a eutectic melt. The results confirm earlier observations of barrel-shaped grains, containing radially oriented subgrains with small-angle misorientations. Two preferred Ni3P–Ni orientation relationships are identified, consolidating apparently contradicting observations in the literature. Considering energetic and kinetic constraints, preferred next-neighbor relations, and the “efficient cluster packing” model, we propose a model for the crystallization micro-mechanism that explains the observed microstructure of partially and completely crystallized Ni–P.

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