Thermal and magnetic properties of bulk glass forming Fe-Al-P-C-B-(Ga) alloys

High-energy ball milling of pre-alloyed ingots, rapid quenching and mechanical alloying of elemental powder mixtures are used to prepare amorphous Fe-Al-P-C-B-(Ga) alloys, which are known to have interesting soft magnetic properties combined with a good glass-forming ability, promising the formation of bulk soft magnetic materials. Pieces of the melt-spun ribbon with a coercivity of are ball milled to investigate the influence of the milling process on the thermal and magnetic properties. X-ray diffraction analysis reveals the amorphous nature of all samples after milling. The samples exhibit a supercooled liquid region varying in the range 44-53 K between the glass-transition temperature and the crystallization temperature . Annealing of the powders was performed in this temperature region to reduce the high stresses induced during milling while maintaining the amorphous structure. The lowest coercivities after annealing of the powders are found to be correlated to the oxygen content. Ball milling of the melt-spun ribbon leads to a slight decrease of the thermal stability, an oxygen content of 0.21 at% and a high of which drops to upon subsequent annealing above . Mechanically alloyed powders with and 1.2 at% oxygen exhibit a coercivity of and a saturation polarization of 1.02 T after heating above to 748 K. The coercivity of found for ball milling of crystalline ingots (0.16 at% oxygen, ) after heating to 703 K is of the same order of magnitude as that of cast amorphous material, which was reported to be 12.7 or . Nonmagnetic inclusions are supposed to lead to the difference in between the as-spun ribbon on the one hand and the ball-milled, mechanically alloyed or cast samples on the other.