Phase formation and magnetic properties of nanocrytalline Ni70Co30 alloy prepared by mechanical alloying

Nanocrystalline Ni70Co30 alloy was synthesized by high energy ball alloying from elemental pure Ni and Co powders as function of milling time. The changes in structural, morphological and magnetic properties of the processed powders during mechanical alloying were characterized respectively by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. X-ray diffraction analysis suggested the formation of two fcc nanostructured solid solutions fcc-Co(Ni) and fcc-Ni(Co), where the crystallite size decreases reaching 4.7-8.0 nm while the microstrain increases up to 0.39-0.42%, due to the severe plastic deformations and the structural defects introduced by milling. Morphological observations indicated a progressive refinement of the particles size with milling time. For longer milling, a narrow particle size distribution with irregular shape was observed. Milling process induced some important changes in the magnetic properties, whereas the variation of the saturation magnetization and coercivity was associated mainly to the particle size refinement, accumulation of microstrain and formation of solid solutions Co(Ni) and Ni(Co). (C) 2020 Elsevier B.V. All rights reserved.