Monitoring the alloying process of mechanically synthesized Fe80Ni20 through changes in magnetic properties

Fe80Ni20 was prepared by mechanical synthesis using a Fritsch Pulverisette Premium (P7) planetary ball mill at 400 RPM. The alloying process was monitored by measuring the magnetic properties of 14 subsamples taken at different milling times (1-2160 min) as well as structural modifications using powder X-ray diffraction and high-resolution imaging. A macroscopically homogeneous body-centered cubic (bcc) alloy with crystallite sizes below 11 nm and microstrain above 1.2% was reached after 960 min (16 h) of milling. The magnetic properties show three distinct stages: (1) the size reduction of the elementary powders, (2) alloying and (3) reduction in particle size of the final alloy.