Magnets with nominal compositions of （ Nd1-x Cex ） 30 Febal Cu0.1 B1 （x = 0, 0.15, 0.3 and 0.4, mass% ） have been fabricated by blending powder method. The remanence （B r）, intrinsic coercivity （He） and maximu...Magnets with nominal compositions of （ Nd1-x Cex ） 30 Febal Cu0.1 B1 （x = 0, 0.15, 0.3 and 0.4, mass% ） have been fabricated by blending powder method. The remanence （B r）, intrinsic coercivity （He） and maximum en- ergy product （BH） of the RE2Fe14B type magnets deteriorated when Nd was replaced by Ce. The chemical composition and crystal structure of magnet were investigated systemically. Backscattered electron （BSE） and energy dispersive spectroscopy （EDS） results revealed that Ce-rich and Ce-lean matrix grains coexisted in the magnets. The magnetic coupling mechanism among the double hard magnetic phases was discussed. Low melting point RE-Cu phase was in favor of the formation of uniform continuous grain boundary. Transmission electron microscopy （TEM） investigation showed the presence of fcc （Nd,Ce）Ox phase in the grain boundary. When the Ce content was 15% of the total amounts of all the rare earth, the maximum energy product of the sintered magnet was 359.8 kJ/ms.展开更多
X-ray diffraction (XRD) and differential scanning calorimetry (DSC) wereemployed to investigate the influence of Ni content on the crystallization of amorphousZr_(70)Cu_(30-x)Ni_x (atom fraction in percent) alloys. Ex...X-ray diffraction (XRD) and differential scanning calorimetry (DSC) wereemployed to investigate the influence of Ni content on the crystallization of amorphousZr_(70)Cu_(30-x)Ni_x (atom fraction in percent) alloys. Experimental results show that with the Nicontent increasing the activation energies for crystallization of amorphous Zr_(70)Cu_(30-x)Ni_xalloys increase correspondingly, indicating that the thermal stability is greatly improved. All theDSC traces of amorphous Zr_(70)Cu_(30-x)Ni_x alloys exhibit two exothermic peaks, suggesting thatthe crystallization process proceeds via a double-stage mode. The first exothermic peak at lowertemperature mainly corresponds to the precipitation and growth of Zr_2Cu particles, while the secondone corresponds to the precipitation of nano-scale Zr_2Ni phase and crystallization of residualamorphous phase. The mechanism on the crystallization of amorphous Zr_(70)Cu_(30-x)Ni_x alloys wasdiscussed.展开更多
The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteri...The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteristics of steel and investigating the impact of anti-corrosion coating on these characteristics. Ablation characteristics were investigated through the macroscopic morphology and x-ray diffraction patterns on the surface of damaged zones, the microstructure and micro Vickers hardness on the cross-section of damaged zones, and the maximum rear-face temperature of sample sheets. It can be concluded that the ablation areas of uncoated sheet consist of the melted layer and the heat-affect layer. These ablation areas include not only the area ablated directly by the arc root, of which the depth is deeper, but also the area forming due to the splashing of molten steel, of which the depth is shallower and decreases when the area’s distance from the arc attachment point increases. For coated sheet, coating materials have decomposed and evaporated forming an ablation pit on the sheet surface, in which the steel surface is exposed, and zinc filler of coating primer has infused into the exposed surface. The ablation diameter of uncoated sheet relates to the amplitude of the 30/80 μs impulse current in quadratic function, while for coated sheet, the relation is linear. In general, under the 30/80 μs impulse current, the coating can decrease the energy injected from the arc to the steel sheet and reduce the melting and splashing of steel. As a result, the ablation severity of uncoated sheet is severer than that of coated sheet.展开更多
基金Item Sponsored by National Natural Science Foundation of China(51171048)National High Technology Research and Development Program of China(2014CB643701)National Science and Technology Support Program of China(2012BAE02B01)
文摘Magnets with nominal compositions of （ Nd1-x Cex ） 30 Febal Cu0.1 B1 （x = 0, 0.15, 0.3 and 0.4, mass% ） have been fabricated by blending powder method. The remanence （B r）, intrinsic coercivity （He） and maximum en- ergy product （BH） of the RE2Fe14B type magnets deteriorated when Nd was replaced by Ce. The chemical composition and crystal structure of magnet were investigated systemically. Backscattered electron （BSE） and energy dispersive spectroscopy （EDS） results revealed that Ce-rich and Ce-lean matrix grains coexisted in the magnets. The magnetic coupling mechanism among the double hard magnetic phases was discussed. Low melting point RE-Cu phase was in favor of the formation of uniform continuous grain boundary. Transmission electron microscopy （TEM） investigation showed the presence of fcc （Nd,Ce）Ox phase in the grain boundary. When the Ce content was 15% of the total amounts of all the rare earth, the maximum energy product of the sintered magnet was 359.8 kJ/ms.
基金This work is financially supported by the National Natural Science Foundation of China (No. 59871025).
文摘X-ray diffraction (XRD) and differential scanning calorimetry (DSC) wereemployed to investigate the influence of Ni content on the crystallization of amorphousZr_(70)Cu_(30-x)Ni_x (atom fraction in percent) alloys. Experimental results show that with the Nicontent increasing the activation energies for crystallization of amorphous Zr_(70)Cu_(30-x)Ni_xalloys increase correspondingly, indicating that the thermal stability is greatly improved. All theDSC traces of amorphous Zr_(70)Cu_(30-x)Ni_x alloys exhibit two exothermic peaks, suggesting thatthe crystallization process proceeds via a double-stage mode. The first exothermic peak at lowertemperature mainly corresponds to the precipitation and growth of Zr_2Cu particles, while the secondone corresponds to the precipitation of nano-scale Zr_2Ni phase and crystallization of residualamorphous phase. The mechanism on the crystallization of amorphous Zr_(70)Cu_(30-x)Ni_x alloys wasdiscussed.
基金supported by National Natural Science Foundation of China (No. 51577117)
文摘The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteristics of steel and investigating the impact of anti-corrosion coating on these characteristics. Ablation characteristics were investigated through the macroscopic morphology and x-ray diffraction patterns on the surface of damaged zones, the microstructure and micro Vickers hardness on the cross-section of damaged zones, and the maximum rear-face temperature of sample sheets. It can be concluded that the ablation areas of uncoated sheet consist of the melted layer and the heat-affect layer. These ablation areas include not only the area ablated directly by the arc root, of which the depth is deeper, but also the area forming due to the splashing of molten steel, of which the depth is shallower and decreases when the area’s distance from the arc attachment point increases. For coated sheet, coating materials have decomposed and evaporated forming an ablation pit on the sheet surface, in which the steel surface is exposed, and zinc filler of coating primer has infused into the exposed surface. The ablation diameter of uncoated sheet relates to the amplitude of the 30/80 μs impulse current in quadratic function, while for coated sheet, the relation is linear. In general, under the 30/80 μs impulse current, the coating can decrease the energy injected from the arc to the steel sheet and reduce the melting and splashing of steel. As a result, the ablation severity of uncoated sheet is severer than that of coated sheet.
