This paper focuses on the preparation of titanium diboride （TiB2） coatings on the graphite substrate by continuous current plating （CCP） and pulse current plating （PIC） electrochemical techniques in fluoride ele...This paper focuses on the preparation of titanium diboride （TiB2） coatings on the graphite substrate by continuous current plating （CCP） and pulse current plating （PIC） electrochemical techniques in fluoride electrolytes （LiF-NaF-KF） containing K2T1F6 and KBF4 as the electrochemically-active components at 700℃. Thick leveled and uniform coatings were obtained and were composed of relatively pure TiB2. The effect of the experimental parameters on the microstructure of the coatings was studied. The results showed the electrodeposition with PIC produced coatings with better quality, when compared with those obtained by CCP, under the conditions of the current density i = 0.6 A/cm^2, frequency = 100 Hz, and todtofr = 4/1. XRD analysis indicated that the preferred orientation of coatings is （110） plane, which is in accordance with the prediction of the two-dimensional crystal nuclei theory. The effect of a ratio of ton/toff and frequency on the crystal size, textule coefficient and microstress was also investigated.展开更多
With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers’ sinter...With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers’ sintering have been investigated. The results show that Zn-Al eutec-toid microstructure can be achieved through their powders’ sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, in which Zn can dissolve into Al whereas Al can hardly dissolve into Zn. During sintering, a diffusion-solution zone a’ has formed and subsequently transformed into a eutectoid microstructure in the cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by the diffusion-solution zone α’. If the diffusion-solution zone α’ is unsaturated, it will have much more crystal defects and the combination between α’ and phase P is weak, thus the process of phase boundary sliding becomes easily; on the展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No. 50204006)
文摘This paper focuses on the preparation of titanium diboride （TiB2） coatings on the graphite substrate by continuous current plating （CCP） and pulse current plating （PIC） electrochemical techniques in fluoride electrolytes （LiF-NaF-KF） containing K2T1F6 and KBF4 as the electrochemically-active components at 700℃. Thick leveled and uniform coatings were obtained and were composed of relatively pure TiB2. The effect of the experimental parameters on the microstructure of the coatings was studied. The results showed the electrodeposition with PIC produced coatings with better quality, when compared with those obtained by CCP, under the conditions of the current density i = 0.6 A/cm^2, frequency = 100 Hz, and todtofr = 4/1. XRD analysis indicated that the preferred orientation of coatings is （110） plane, which is in accordance with the prediction of the two-dimensional crystal nuclei theory. The effect of a ratio of ton/toff and frequency on the crystal size, textule coefficient and microstress was also investigated.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 59871031 and 59871025).
文摘With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers’ sintering have been investigated. The results show that Zn-Al eutec-toid microstructure can be achieved through their powders’ sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, in which Zn can dissolve into Al whereas Al can hardly dissolve into Zn. During sintering, a diffusion-solution zone a’ has formed and subsequently transformed into a eutectoid microstructure in the cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by the diffusion-solution zone α’. If the diffusion-solution zone α’ is unsaturated, it will have much more crystal defects and the combination between α’ and phase P is weak, thus the process of phase boundary sliding becomes easily; on the
