| Fe-based amorphous/nanocrystalline alloy have been widely used in industrial products, such as sensors,transformers, motors and telecommunication equipment and other fields, due to their outstanding properties as soft magnetic materials, such as high saturation magnetization, low coercive force and high initial permeability. Moreover, in the power system, it is the ideal green material instead of silicon steel, which has attracted considerable attention. However, compared to the Zr-based, Pt-based and Ni-based alloys,Fe-based alloy has a poor glass forming ability and depends on the addition of metalloid elements (B, Si, P etc.). Some researches have pointed out that the soft magnetic properties and brittleness at room temperature of Fe-based amorphous alloy are closely related to the type, content and distribution of metalloids. Therefore, reducing the content of metalloids and improving the content of ferromagnetic elements, developing a new type of metalloid-free Fe-based amorphous alloy with excellent soft magnetic properties has a very important application and academic significance.A series of high-iron Fe-(Zr. Hf)-(B, Si), Fe-M-Si-B amorphous alloy ribbons containing a little metalloid and metalloid-free (Fe, Co, Ni)-TM-X amorphous alloy ribbons were prepared by single roller melt-spinning method using Inoue empirical criterion, similar element substitution method and trace element addition method. The phase structure and soft magnetic properties of the as-prepared samples were measured and characterized by XRD, DSC, VSM, soft magnetic dc B-H loop tracer and other testing methods. The variation of phase structure and soft magnetic properties of Cu-doped (Fe, Co)-Hf-Zr-B amorphous alloys were studied by microalloying technique. At the same time, the glass forming ability (GFA), crystallization kinetics, crystallization phase and soft magnetic properties before and after annealing of these two new metalloid-free high-iron Fe-based amorphous alloys were investigated, and compared with the same type of Fe-based amorphous alloys containing a small amount of metalloid. The following experiments were carried out:1) Effects of Hf substituted for Zr on the GFA, thermal stability and soft magnetic properties in the high-iron Fe90Zr7-xHfxB3 (x = 0, 1,2, 3, 4, 5, 6, 7) alloys were investigated.The results show that with the addition of Hf element, the amorphous structure forms in alloys, the temperature interval between the first and the second onset crystallization temperature (△T = Tx2-Tx1) increases,and the thermal stability increases gradually. The AT values of Fe90Zr7-xHfxB3 alloys is in the range of 230 ～260 ℃,which is higher than that of other Fe-based amorphous alloy, showing more excellent thermal stability and wider heat treatment temperature range. However, the soft magnetic properties of this alloy in the as-quenched state is relatively poor, but annealing can greatly optimize its soft magnetic properties.2) Effects of Si content on the GFA and soft magnetic properties of Fe90-xZr10Six (x ＝1, 2, 3, 4, 5, 10) alloys were investigated. The results show that the GFA of the alloys are obviously different with the addition of different Si content. In general, the GFA of the alloy is weak and depends on the content of Si element. The amorphous structure just formed in Fe87Zr10Si3 alloy. The △T value is 169.1 ℃. slightly lower than that of Fe-(Zr,Hf)-B alloys, indicating that the thermal stability is worse than that of Fe-(Zr. Hf)-B alloys,but the soft magnetic properties are better. In Fe87Zr10Si3 amorphous alloy, the saturation magnetization (Ms) is equal to 111.4 emu/g and the coercive force (Hc) is equal to 39.1 A/m.3) Effects of different transition metal elements M on the GFA and soft magnetic properties of Fe84M3B8Si5 (M = Ti, Zr, Mo, Hf, and Nb) alloys were studied. The results show that the GFA of Fe84B8Si5EM3 (EM = Ti,Zr,Mo,and Hf) alloys show obvious difference. The addition of Mo and Hf is more favorable for the formation of Fe84M3B8Sis amorphous alloys. In Fe84Mo3B8Si5 and Fe84Hf3B8Sis alloys, the △T value reaches maximum of about 298 ℃ exhibiting the most excellent thermal stability. In general,Fe84M3B8Si5 alloys show good soft magnetic properties. Fe84Mo3B8Si5 alloy with amorphous structure has the best soft magnetic properties, the Ms is equal to 152.8 emu/g and the Hc is equal to 11.3 A/m. When annealed at 550～650 ℃, the Ms values of Fe84M3B8Si5 (M = Zr,Mo, Hf) alloys change in the range of 177.0～195.7 emu/g.4) Effects of Co substituted for Fe on the GFA, thermal stability and soft magnetic properties of Fe85-xCoxHf8Zr1B6 (x = 0, 10, 20, 30, 40) alloys were investigated. The results show that the addition of Co element at 10～30 at.% improves the GFA and thermal stability of the alloy system. The Ms of the as-quenched FessHf8Zr1B6 alloy ribbon is only 59.2 emu/g and the Hc is 2.9 A/m. After adding Co element, the Ms of the as-quenched alloys increases greatly and reaches the maximum of about 124.0 emu/g when the Co content is 20 at.%.5) Effects of Cu-doped on the precipitation and soft magnetic properties before and after annealing of Fe65CO20Hf8Zr1B6 amorphous alloys were investigated. The results show that the as-quenched Fe64.5Co20Hf8Zr1B6Cu0.5 amorphous alloy exhibits the best soft magnetic properties, the Ms is equal to 116.4 emu/g and Hc is 6.9 A/m. However, after annealing at 550 ℃, Fe63Co20Hf8Zr1B6Cu2 amorphous alloy exhibits the best soft magnetic properties, the Ms reaches the maximum value of about 139.2 emu/g, while the Hc remains low value of about 7.8 A/m.6) The metalloid-free (Fe1-x-yCoxNiy)72Cr15Zr10W3 (x,y = 0,0.25) amorphous alloys were prepared on the basis of the previous study. The results show that when x is equal to 0.25 and y is equal to 0.25, the fully amorphous structure is formed and the Hc is about 5.0 A/m. The apparent activation energy (E) for onset crystallization temperature Ex(K) and crystallization peak temperature Ep(K) are calculated to be Ex(K) = 331.8 kJ/mol and EP(K)=255.5 kJ/mol, respectively, by using Kissinger equation. E can also be determined by Ozawa equation, which gives the values of Ex(O) = 329.7 kJ/mol and Ep(O) = 246.9 kJ/mol,respectively. The activation energy calculated by the two models is very close. Moreover,the relationship curves between the crystallization volume fraction (x) and the temperature of the amorphous alloy show a sigmoid shape (S-type). With the increase of the heating rate,the relationship curves move obviously to the high temperature region.7) The metalloid-free Fe89Hf7Zr1Al3 amorphous alloy ribbon with high iron content was prepared successfully and compared with Fe89Hf7Zr1B3 alloy ribbons containing a small amount of metalloids. The results show that the metalloid-free Fe89Hf7Zr1Al3 alloy and Fe89Hf7Zr1B3 alloy containing 3 at.% metalloid element B can form completely amorphous structure. Two obvious exothermic peaks appear on the DSC curves of the two amorphous alloys, while the △T value of Fe89Hf7Zr1Al3 amorphous alloy is 50.7 ℃, significantly lower than 200.8 ℃ of Fe89Hf7Zr1B3 amorphous alloy. This indicates that the thermal stability of the amorphous alloy tends to decrease when X changes from a metalloid element to a metal element.8) The crystallization kinetics and soft magnetic properties of Fe89Hf7Zr1Al3 and Fe89Hf7Zr1B3 amorphous alloys were analyzed and compared. The results show that the apparent activation energy of Fe89Hf7Zr1B3 and Fe89Hf7Zr1Al3 amorphous alloys calculated by Kissinger equation and Ozawa equation shows the same trend,that is,Ep2 > Ex2 > Ep 1 >Ex1. In the as-quenched state, Fe89Hf7Zr1Al3 amorphous alloy exhibits excellent soft magnetic properties, the Ms is 165.1 emu/g, the H, is 4.3 A/m, and the T, is 336.6 ℃; while the Fe89Hf7Zr1B3 alloy possesses poor soft magnetic properties, the Ms is 65.8 emu/g, the Hc is 17.4 A/m and the Tc is 326.8 ℃. When annealed at 375 ℃, the Fe89Hf7Zr1Al3 alloy has the best soft magnetic properties, the M5 and Hc is about 165.3 emu/g and 3.5 A/m,respectively. But the Fe89Hf7Zr1B3 alloy is dependent on high temperature annealing treatment to optimize its soft magnetic properties. |
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