Jiawei Li

Soft-ferromagnetic bulk glassy alloys with large magnetostriction and high glass-forming ability

The effect of Dy addition on the glass-forming ability(GFA),magnetostriction as well as soft-magnetic properties and fracture strength in FeDyBSiNb glassy alloys was investigated. In addition to the increase of supercooled liquid region from 55 to 100 K, the addition of Dy is effective in approaching alloy to an eutectic point and increasing the saturation magnetostrction (λ s ). Accordingly, bulk glassy alloy (BGA) rods with diameters up to 4 mm were produced, which exhibit a large λ s as high as 65×10-6. Besides, the BGA system exhibits superhigh fracture strength of 4000 MPa, combined with good soft-magnetic properties.

High-entropy bulk metallic glasses as promising magnetic refrigerants

In this paper, the Ho20Er20Co20Al20RE20 (REu2009=u2009Gd, Dy, and Tm) high-entropy bulk metallic glasses (HE-BMGs) with good magnetocaloric properties are fabricated successfully. The HE-BMGs exhibit a second-order magnetic phase transition. The peak of magnetic entropy change ( ΔSMpk) and refrigerant capacity (RC) reaches 15.0u2009J kg−1 K−1 and 627u2009J kg−1 at 5u2009T, respectively, which is larger than most rare earth based BMGs. The heterogeneous nature of glasses also contributes to the large ΔSMpk and RC. In addition, the magnetic ordering temperature, ΔSMpk and RC can be widely tuned by alloying different rare earth elements. These results suggest that the HE-BMGs are promising magnetic refrigerant at low temperatures.

Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

The effects of heavy rare earth (RE) additions on the Curie temperature (T-C) and magnetocaloric effect of the Fe-RE-B-Nb (RE-Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T-C in a large temperature range of 120K without significantly decreasing the magnetic entropy change (Delta S-M) and refrigerant capacity (RC) of the alloys. The observed values of Delta S-M and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd5Ge1.9Si2Fe0.1. The tunable T-C and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

Fe-based amorphous coating with high corrosion and wear resistance

The amorphous coating with a new developed composition of Fe63Cr8Mo3.5Ni5P10B4C4Si2.5 has been successfully prepared by high velocity oxygen fuel technique. The amorphous coating shows good corrosion and wear resistance, which compare favourably with those of the well-known SAM1651 (Fe48Mo14Cr15Y2C15B6) and SAM2X5 (Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) amorphous coatings despite the absence of W, and very low Cr and Mo content. The electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis reveal that under high passive potentials the passive film on the coating reflects bi-layer structure and transpassive dissolution occurs, but the film can still remain passive due to slow ionic transport under these conditions. Donor densities of the passive films on the coatings are in the order of magnitude of 1021u2005cm−3 which is comparable to the reported values for passive films of SAM series amorphous coatings indicating the approximate stability of the passive film. In addition, the dominating wear mechanism of Fe-based amorphous coatings is oxidation wear. GRAPHICAL ABSTRACT

Thin and Flexible Fe–Si–B/Ni–Cu–P Metallic Glass Multilayer Composites for Efficient Electromagnetic Interference Shielding

Thin and flexible materials that can provide efficient electromagnetic interference (EMI) shielding are urgently needed, especially if they can be easily processed and withstand harsh environments. Herein, layer-structured Fe-Si-B/Ni-Cu-P metallic glass composites have been developed by simple electroless plating Ni-Cu-P coating on commercial Fe-Si-B metallic glasses. The 0.1 mm-thick composite shows EMI shielding effectiveness of 40 dB over the X-band frequency range, which is higher than those of traditional metals, metal oxides, and their polymer composites of larger thickness. Most of the applied electromagnetic waves are proved to be absorbed rather than bounced back. This performance originates from the combination of a superior soft magnetic property, excellent electrical conductivity, and multiple internal reflections from multilayer composites. In addition, the flexible composites also exhibit good corrosion resistance, high thermal stability, and excellent tensile strength, making them suitable for EMI shielding in harsh chemical or thermal environments.

Effects of W Addition on the Electrochemical Behaviour and Passive Film Properties of Fe-Based Amorphous Alloys in Acetic Acid Solution

The electrochemical behaviour and passive film properties of Fe–Cr–Mo–W–C–B–Y amorphous alloys in acetic acid solution were investigated. The potentiodynamic polarisation and Nyquist curves demonstrated that W addition significantly enhanced the corrosion resistance. Mott–Schottky plots and angle-resolved X-ray photoelectron spectra indicated that passive films with different W contents exhibited dipolar (p–n) semiconducting characteristics separated by flat-band potentials. The outer and inner oxide layers of the passive films were modified by reducing the acceptor and donor densities. Moreover, W addition favoured the formation of a thicker and more stable passive film to inhibit the dissolution of alloy elements.