Jie Song
材料科学技术（英文）
Magnesium-substituted MnZn ferrites with composition of Mn0:4Zn0:6MgxFe(2-x)O4 (x=0.00, 0.05) were prepared by citrate-EDTA (ethylenediamine tetraacetic acid) complexing method. The crystal structure, surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and network analyzer (Agilent 8722ET). All the XRD patterns showed the single phase of the spinel-type MnZn ferrite without other intermediate phase. The lattice parameter and average particle size increased with the substitution of magnesium. The microwave electromagnetic properties of the samples have been studied at the frequency range from 2 to 18 GHz. It was shown that the values of ε' and ε' ' decreased slightly with the substitution of magnesium. The values of μ' and μ'' were improved significantly, and the peak of μ'' shifted to low frequency with Mg2+ ions substituting. Furthermore, the reasons have also been discussed by using electromagnetic theory. The reflection loss (RL) ascended after magnesium was substituted. Magnesium-substituted ferrite had excellent microwave absorption properties. The frequency (with respect to -10 dB) started from 11.3 GHz, and the bandwidth reached about 3.5 GHz. The peak value of RL was about -19 dB at a matching thickness of 3.1 mm.
关键词:
Mn-Zn ferrite
,
Citrate-EDTA
,
Magnesium
,
Microwave absorbing properties
H. Jafari
金属学报(英文版)
doi:10.1016/S1006-7191(08)60115-5
Due to their high specifc strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two diferent thermomechanical treatments (TMTs). For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of the Beta-phase (Mg17Al12) in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.
关键词:
Thermomechanical treatment
,
Magnesium
,
Cold work
,
Aging
,
AZ63
