Amorphous to crystalline transformation in bulk electroless nickel by differential scanning calorimetry

Abstract

Differential scanning calorimetry (DSC) in conjunction with X-rays and transmission electron microscopy were employed to elucidate the mechanism of amorphous to crystalline transformation in bulk electroless nickel (Ni—10.9 wt. % P) alloy. As-deposited amorphous electroless nickel was heated from room temperature to 650°C in a DSC cell in an argon atmosphere at 20°C min −1. Three exothermic reactions were observed. Heating runs were interrupted after each reaction for microstructural and crystal structure determinations. It was found that the first reaction was associated with the precipitation of fine nickel particles in an amorphous Ni 3P matrix, the second with crystallization of the amorphous Ni 3P matrix into spherulitic grains, and the third with recrystallization and grain growth of the Ni 3P matrix and coarsening of nickel precipitates. The transformation temperatures and heats of reaction were also determined. This demonstrates the application of high sensitivity differential scanning calorimetry to the study of solid state reactions in general.