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Su X.,Jiangsu Polytechnic University | Su X.,Xiangtan University | Liu Y.,Xiangtan University | Liu D.Y.H.,Teck Metals Ltd. | And 3 more authors.
Journal of Alloys and Compounds | Year: 2010

Experiments were carefully planned and executed in this systematic study of the phase equilibria in the Zn-Cr binary system. A lone intermetallic compound, CrZn17, was found in the system. Based on the new findings and reliable data from open literature, the thermodynamic description of the Zn-Cr binary system was optimized, and a set of self-consistent thermodynamic parameters was obtained. The calculated phase diagram agreed well with experimental results. © 2010 Elsevier B.V. All rights reserved. Source

Wu C.,Changzhou University | Wu C.,Xiangtan University | Su X.,Changzhou University | Su X.,Xiangtan University | And 5 more authors.
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2011

Experimental investigation followed by thermodynamic assessment of the VZn system was carried out in the present study. A series of VZn alloys annealed at various temperatures were examined using scanning electron microscopy coupled with energy dispersive spectroscopy/wavelength dispersive X-ray spectrometer, X-ray diffraction and differential thermal analysis. It was confirmed that V Zn16, with a V content of about 5.8 at.%, was indeed an equilibrium phase. DTA results indicated that the peritectic temperature for V Zn 16 was about 427 °C. Two new metastable compounds, V Zn9 and V 3Zn2, with V contents of 8.511.3 at.% and 60 at.%, respectively, were discovered. DTA results together with SEM-EDS examinations revealed that V Zn9 was formed at around 450 °C in Zn75V25 alloy with a cooling rate greater than 12 °Cmin. The V Zn9 phase, however, decomposed into V Zn3 and liquid Zn when the alloy was held above 442 °C. The peritectic temperatures for two equilibrium phases, V 4Zn5 and V Zn3, were 651 °C and 621 °C, respectively. These measurements were slightly lower than the values determined in prior studies. The onset temperature for forming V Zn3 decreased significantly with increasing cooling rate while its exothermic peak widened during fast cooling. These phenomena indicated that both the nucleation and growth processes for V Zn3 were kinetically challenged. In addition, the solubility of Zn in α-V was measured. It was 2.1 at.%, 2.5 at.%, 2.6 at.%, 2.9 at.% and 3.3 at.% at 450 °C, 600 °C, 670 °C, 800 °C and 1000 °C, respectively. Based on the results obtained in the present study and previous investigations, the VZn system was reassessed thermodynamically. The assessment was in good agreement with experimental results. © 2011 Elsevier Ltd. All rights reserved. Source

Wu C.,Xiangtan University | Su X.,Xiangtan University | Su X.,Changzhou University | Liu D.,Teck Metals Ltd. | And 4 more authors.
International Journal of Materials Research | Year: 2010

The 450°C isothermal section of the Zn-Fe-V ternary phase diagram has been determined experimentally using X-ray diffraction and scanning electron microscopy coupled with energy/wave dispersive spectroscopy. A new ternary compound T, containing 1.4 to 4.5 at.% V, 5.6 to 15.5 at.% Fe and 82.3 to 92.2 at.% Zn, was positively identified for the first time in this study. The existence of the rphase, together with two Zn-V compounds, VZn3 and V4Zn5, at 450°C has been confirmed. Fe has no detectable solubility in Zn-V compounds. But it was proved that about 3.0 at.% Zn can dissolve into α-V at 450°C. Experimental results indicated that the maximum solubility of V in δ, Γ1, and C was 0.5 at.%, 1.3 at.% and 1.8 at.% respectively, whereas that in ζ was less than 0.2 at.%. © Carl Hanser Verlag GmbH & Co. KG ISSN 1862-5282. Source

Wu C.,Xiangtan University | Wang X.,Xiangtan University | Liu D.,Teck Metals Ltd. | Li Z.,Xiangtan University | And 4 more authors.
Journal of Phase Equilibria and Diffusion | Year: 2011

The phase relationships in the Zn-rich corner of the Zn-Fe-Zr system at 450, 600 and 800 °C were investigated by means of x-ray powder diffraction (XRD) and scanning electron microscopy coupled with energy/wave dispersive spectroscopy (SEM-EDS/WDS). Two ternary compounds were found in the system. One of them was designated as ZrFe 2Zn 20 according its narrow composition range. It is a CeCr 2Al 20-type compound with lattice parameter a = 1.3941 nm. ZrFe 2Zn 20 is stable below 878.6 °C and can co-exist with all binary compounds in the Zn rich corner of the system. The other one was designated as Zr 2Fe 3Zn 5. SEM-WDS analysis indicated that Fe was hardly detected in ZrZn 22, Zr 5Zn 39 and ZrZn 3. And no Zr was dissolved in all Fe-Zn intermetallic compounds. © 2011 ASM International. Source

Su X.,Changzhou University | Su X.,Xiangtan University | Wu C.,Xiangtan University | Liu D.,Teck Metals Ltd. | And 3 more authors.
Surface and Coatings Technology | Year: 2010

In the present study, the effect of V additions to the galvanizing bath on the microstructure and growth kinetics of the galvanized coating on Si-containing steels was experimentally investigated. Three different steels with effective Si contents of 0.158, 0.242 and 0.363. wt.%, were immersed for 0.5 to 8. min in Zn baths with four levels of V, ranging from 0 to 0.16. wt.%. The results indicated that V additions could adequately suppress the Si reactivity of all three steels. The potency of V increased with its increasing content in the bath. Crystallites of a ternary compound were found at the ζ/liquid interface.Based on the isotherms of Zn-Fe-V and Zn-Fe-Si-V systems at 450 °C, a diffusion path model was proposed to interpret the effect of V on galvanizing pure Fe or Si-containing steels. V in the bath introduced a new equilibrium state between the liquid and a ternary phase T and made the equilibrium state between the liquid-ζ phases metastable. Furthermore, the greater solubility of Si in T made the diffusion path more difficult to enter the (ζ + T. + Liq.+ FeSi) region and, thus, protected the integrity of a normal coating. © 2010. Source

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