Yaqiang Dong

Giant magnetoimpedance effect enhanced by thermoplastic drawing

We performed thermoplastic forming (TPF) on FeCoNbB metallic glass ribbons with a supercooled liquid region exceeding 100 K, and found the sample after TPF is still completely amorphous. More importantly, the giant magnetoimpedance (GMI) effect was improved after the forming process: the maximum GMI ratio and sensitivity increased from 41% to 12.3%/Oe in the case of as-cast sample to 280% and 358.2%/Oe in the case of resulting sample after TPF, respectively. The hysteresis loops and domain patterns were subsequently studied, which revealed that the primary factor leading to the improvement of the GMI effect was the enhanced longitudinal magnetic anisotropy induced by the TPF process. We therefore assume that TPF is an effective way that improves the GMI effect, which differs from conventional annealing methods.

The soft magnetic properties of ring-shaped (Co0.6Fe0.3Ni0.1)68(B0.811Si0.189)27Nb5 bulk metallic glasses

Ring-shaped (Co0.6Fe0.3Ni0.1)68(B0.811Si0.189)27Nb5 bulk samples with an outer diameter of 10 mm, an inner diameter of 6 mm, and a thickness of 1 mm were successfully prepared by copper mold casting. The effects of annealing treatments on magnetic properties of the ring-shaped bulk sample were investigated. After the optimum annealing treatment, the resulting ring-shaped bulk sample exhibits good magnetic properties, i.e., low coercive force of 0.55 A/m, high maximum permeability of 433 000, and high permeability of 19 400 at 50 Hz under an AC field amplitude of 1.2 A/m, respectively. In addition, the ring-shaped bulk sample also shows low core loss of 0.09 W/kg at 50 Hz under induction of 0.5 T. The synthesis of ring-shaped bulk samples with good magnetic properties is encouraging for their potential applications as functional materials in the future.

Effect of Nb Addition on the Glass-forming Ability,Soft-magnetic Properties and Mechanical Properties of CoFeNiBSiNb Bulk Glassy Alloys

The effect of Nb addition on the glass-forming ability (GFA), soft-magnetic properties and mechanical properties of [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx(x=36) alloy system were investigated. The results showed that by adjusting the content of Nb, the thermal stability of the supercooled liquid and the GFA increased effectively. With increasing the amount of Nb, the supercooled liquid region (ΔTx) increased from 45 to 65 K and the reduced glass transition temperature (Trg=Tg/Tl) was located in the range of 0.5840.644. As a result, the [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx bulk glassy alloys (BGAs) with diameters up to 5.0 mm were produced by copper mold casting. In addition to the high GFA, the Co-based glassy alloys exhibited excellent soft-magnetic properties, i.e., saturation magnetization of 0.530.81 T, low coercive force of 0.511.75 A/m, and high effective permeability of (1.522.53)×104 at 1 kHz under a field of 1 A/m. Besides, the Co-based BGAs also exhibited super high fracture strength of 42704490 MPa and vickers hardness of 11271182.