Papers by Author: Jun Hua You

Abstract: The microstructures and phase constituent of as-cast Mg-5Sn-5Zn-xSr (x=0, 0.5, 1, 2) alloys were analyzed by the optical microscopy (OM), the scanning electron microscope (SEM) and the X-ray diffraction (XRD). The results indicate that an addition of 0.5%-2% (mass fraction) Sr to the Mg-5Zn-5Sn alloy not only refines the dendrite arm spacing of -Mg but also results in the formation of MgSnSr phases. Furthermore, it was found that the increase of Sr results in Mg2Sn phase decreasing and MgSnSr phase increasing. While the MgZn phase which is attached with Mg2Sn phase exists in the form of -Mg+MgZn eutectic structure.

Abstract: The Fe-Si-Al soft magnetic composites were produced by cold pressing of water-atomized Fe-Si-Al powder using organic binder. The effect of shaping pressure, annealing temperature, magnetic annealing and dielectric content on properties of Fe-Si-Al soft magnetic composites was investigated. The results showed that increasing shaping pressure increases density and radial crushing strength of Fe-Si-Al soft magnetic cores, and decreases coercivity and total loss. Increasing annealing temperature can increase effective permeability and decrease total loss owing to decreasing hysteresis loss, and over-annealing (＞660°C) can deteriorate magnetic properties. The magnetic annealing can decrease total loss of Fe-Si-Al magnetic powder core. Increasing dielectric content can reduce the eddy current loss of Fe-Si-Al magnetic powder core and decrease the real part of permeability. Fe-Si-Al magnetic powder core with shaping pressure of 1800 MPa, annealing temperature of 660 °C and dielelctric content of 0.7% presented the optimum magnetic properties with an effective permeability of 127, a total loss of 78mW/cm3 and a radial crushing strength of 18MPa.