Effects of Al on the crystallisation and magnetic properties of amorphous Fe-B-Si alloys

Abstract

Magnetisation and ⁵⁷Fe Mossbauer effect measurements have been made for the Fe₈₀B₁₂Si_8-xAl_x (x=0, 3, 6) alloys in the amorphous state. For the alloy with x=0 the most probable Fe hyperfine field at 77K is 285+or-6 kOe. This value shows a slight decrease as Si is replaced by Al. The Fe moment is (1.83+or-0.03) mu _B for the alloy with x=0 and increases by approximately 0.013 mu _B per at.% Al. Differential thermal analysis (DTA) measurements show that there are two stages of crystallisation in all the alloys. The alloys with x=0 show crystallisation processes at 763+or-5 and 812+or-5K. The addition of Al to the alloy decreases the temperature of the lower-temperature peak by approximately 10K per at.%Al and of the higher-temperature peak by approximately 2.7K per at.%Al. X-ray diffraction and Mossbauer effect measurements of partially and fully crystallised samples indicate that the lower-temperature peak results from the precipitation of BCC Fe-(Si,Al) and that the higher-temperature peak results from the precipitation of Fe₂B as well as additional BCC Fe-(Si,Al).