Magnetic and microstructural properties of nanocrystalline Fe-25 at% Al and Fe-25 at% Al+0.2 at%B alloys prepared by mechanical alloying process

In the present work, structural and magnetic properties of nanocrystalline Fe-25at%Al and Fe25at% Al+0.02at%B alloys produced by mechanical alloying were studied. Their microstructural properties were investigated by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. A BCC-nanostructured Fe(Al,B) solid solution with an average crystallite size of about 18nm has been produced by milling for 4 h. Whereas in Fe-25at%Al the alloying process has been accomplished after 16 h of milling. It is found that B speeds up the formation of a bcc phase with finer microstructure (around 5 nm) after 40 h of milling. When increasing the milling time, the crystallite size decreases for all powders. An increase in microstrain was observed with increasing the milling time and also with addition of boron. Coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting saturation magnetization and coercivity (H-c) in both alloys. These variations are explained by crystallite size and strain variations in the samples during milling.