Herein, SnO2- and ZnO2-doped (1.5 wt.%) composite Cu powder was prepared by mechanical alloying (MA) respectively, and both the contact materials of oxide-doped Cu alloys were subsequently obtained by canned hot-pressing powder sintering with hot extrusion combined. Scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM) and self-designed electrical breakdown device were used for investigating the microstructure and properties including electric conductivity and hardness, especially for electrical contact performance of the Cu-SnO2 alloy and in compared with the Cu-ZnO2 alloy. The experimental results show that the hardness of Cu-SnO2 and Cu-ZnO2 contact materials are 103.5±1 HV and 192.7±1 HV, respectively, which meet the hardness standard of national standard electrical contact materials. Meanwhile, the relative conductivity %IACS are 7.24% and 6.20%, respectively, which are higher than the traditional Cu-based contact materials. This electrical life simulation test system was designed independently, and the results indicate that the switching times of Cu-SnO2 contact materials are much more than that of Cu-ZnO2. The addition of SnO2 can effectively improve the arc extinguishing characteristics and the anti-welding performance of the contact materials is enhanced. In summary, SnO2-doped Cu-based contact materials possess excellent comprehensive properties, which can provide reference for potential applications in contact materials.

Droplet flight and solidification behaviors during twin-wire arc sprayed (TWAS) composite coatings were systematically investigated. Both theoretical model and numerical method were established for calculating the droplet deformation, breakup and solidification process in air flow based on the volume of fluid (VOF) dual-phase flow model jointed with the standard k-ε model. The experimental simulation results indicate that TWAS droplet is broken through explosion or two steps breaking process. The calculation of TWAS gas flight dynamics demonstrates that the TWAS particles are accelerated at first and then slowed down. Microstructure of the TWAS prepared Ni-5wt.%Al and Ni-20wt.%Al composite coating was accordingly characterized by XRD, SEM and TEM, so the phase compositions of the Ni-Al composite coatings were obtained. TEM analysis also showed that an amorphous phase was formed according to the characteristic of diffraction ring in Ni matrix solid solution at an original state.

We here report on a comparative study of the microstructure and magnetic properties of as-cast and SPCJA-ed Co-based wires for potential sensor applications. Experimental results indicate that both as-cast and SPCJA-ed wires exhibit typical amorphous feature. There also exists the enhanced local ordering degree of atomic arrangement and obvious transformation (maximum magnetic permeability and minimum saturation magnetization) of magnetic properties after SPCJA treatment, resulting from variation of magnetic moment exchange coupling and magnetic anisotropy by coactions of high-density pulsed magnetic field energy and thermal activation energy. Moreover, SPCJA treatment can drastically improve the GMI property of melt-extracted wires. GMI ratio [ΔZ/Z0]max of 166.07% and field response sensitivity ξmax of 413.76%/Oe by more than 2.25 times and 1.73 times of as-cast wire at 5MHz. Therefore, the SPCJA-ed wire exhibits the improved GMI and magnetic properties at 5MHz~10MHz in contrast to AC annealed wire, which is more suitable for GMI sensor applications working at low-applied-frequency and relatively low-working-magnetic field.

The Gd55Al20Co25 amorphous wires exhibit a relatively strong magnetocaloric effect (MCE). These melt-extracted amorphous wires display second-order magnetic transition (SOMT) and the value of maximal magnetic entropy (–ΔSm) for the melt-extracted wires is calculated to be ~9.7 J·kg–1·K–1 around the Curie point (TC) of ~110 K with applied field of 5 T. Moreover, the melt-extracted amorphous wires show a high refrigerating efficiency with a relatively large cooling power (RCP, ~804 J·kg–1) and refrigeration capacity (RC, ~580 J·kg–1) under an applied magnetic field of 5T due to the broad paramagnetic-ferromagnetic (PM-FM) region associated with amorphous alloys. These favorable properties make melt-extracted Gd-based amorphous wires to be the potential refrigerant for magnetic refrigeration (MR) of liquid oxygen.

Giant magneto-impedance (GMI) effect and domain transformation for melt-extracted Co68.15Fe4.35Si12.25B13.25Nb1Cu1 amorphous wires have been induced by a cryogenic Joule annealing (CJA) treatment with different DC current amplitude (0~350 mA) for 240s. Experimental results indicate that the maximum GMI ratio ([ΔΖ∕Ζ0]max) achieves to 188.1% with exciting field increasing to 1.8 Oe monotonically for 300 mA annealing treated wires, which can attribute to the surface complex domain structure change formed by CJA treatment. The liquid nitrogen can protect the wire from crystallization when applied large DC currents. Moreover, the CJA treatment can improve the response sensitivities effectively. These remarkable characteristics make the melt-extracted microwires by CJA tailoring as the promising candidate material for small-sized magnetic sensors.

Gd60Al20Co20 amorphous wires with smooth surfaces and circular cross-sections were fabricated by a melt-extraction technique. The mechanical properties of the extracted microwires were evaluated by tensile tests and their fracture reliability was estimated by using Lognormal and two- or three- parameter Weibull analysis, respectively. The microwires exhibit a tensile fracture strength ranging from ~788 to ~1196 MPa, with a mean value of 1008 MPa and a standard variance of 121 MPa. Lognormal method of statistical analysis presents that the average stress of microwires is ~1012 MPa. Weibull statistical analysis indicates that the two-parameter tensile Weibull modulus is 8.5 and the three-parameter Weibull modulus is 5.3 with a threshold value ~365 MPa for as-extracted amorphous microwires. Our results show that the extracted Gd-based wires possess excellent tensile properties and high fracture reliability, with a high potential for applications in and magnetic refrigeration.

Ni48Mn26.4Ga19.7Fe5.9 microwires with grain size of 1-3 micron were successfully fabricated by melt-extraction. The superelastic effects in the microwires under various temperatures and loads were systematically demonstrated. The as-extracted microwires displayed partial superelasticity when attended at relatively high temperature. The critical stress for stress-induced martensite formation increases linearly with temperature and follows the Clausius-Clapeyron relationship. The temperature dependence of the as-extracted polycrystalline Ni48Mn26.4Ga19.7Fe5.9 microwires is 16.4 MPa/K, which is higher compared with Ni-Mn-Ga single crystals. In addition, the as-extracted microwires display excellent shape memory behavior with the recovery strain and recovery ratio of 1.26% and 86%, respectively, when the total strain reaches 1.47% at 310 K.