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Li C.,Shanghai University | Li M.,Shanghai University | Zhang H.,Shanghai University | Ali W.,Shanghai University | And 6 more authors.
Surface and Coatings Technology | Year: 2017

The investment casting is one of the most versatile modern technique for metal forming, however, the high chemical stability of ceramic shell materials is required due to the high activity of titanium melt. The Al2O3 is one kind of the common refractory material, which can not be directly used for casting titanium alloys because of its reaction with the melt and contamination caused by this reaction. In this paper, the Y2O3 doped BaZrO3 coating was fabricated on the Al2O3 matrix in order to develop a novel casting and directional solidification technology. Using the Al2O3 as the matrix, the Y2O3 doped BaZrO3 coating was prepared by smearing the slurry, dusting the BaZrO3 powder and sintering them. The reaction between the Al2O3 matrix and the protective coating, the surface quality and chemical stability of the Y2O3 doped BaZrO3 coating were investigated using the optical microscope (OM), energy dispersive spectrometer (EDS) and scanning electronic microscope (SEM), respectively. Afterward, the interaction between Y2O3 doped BaZrO3 coating and titanium melt was discussed. Optical microscope and SEM results showed that the BaZrO3 coating possessed the good surface morphology and high chemical stability, and EDS results showed the thickness of interaction layer between the Al2O3 matrix and the protective coating did not vary with the sintering time and temperature (at 1500°C and 1600°C for 2, 4 and 6h). The thickness of diffusion layer was 10μm for the rod of Ti-46Al-8Nb with the directional solidification, the same was the counterpart for the casting part of Ti-6Al-4V alloy. This may imply that Y2O3 doped BaZrO3 is a promising coating for the solidification of titanium alloy. © 2017 Elsevier B.V.


Jiang M.,Shanghai University | Jiang M.,Baosteel | Chen L.-N.,Shanghai University | He J.,Shanghai University | And 5 more authors.
Advances in Manufacturing | Year: 2014

The study of controlled rolling/controlled cooling process parameters which affect the microstructure and mechanical properties of a novel pipeline steel have been optimized by the orthogonal experiment with four factors and three levels in this paper. However, the parameters of thermo-mechanical control process (TMCP) optimized by the Gleeble-3500 hot simulator could not satisfy performance requirements of the X100 pipeline steel. In order to improve the performance of this steel, the influence of finish cooling temperature (FCT) on the microstructure and property is studied in detail. It is found that, as this steel is thermo-mechanically treated by this set of parameters (the start heating temperature, finish rolling temperature (FRT), FCT and cooling rate of 1,180 ˚C, 810 ˚C, 350 ˚C and 35 ˚C/s, respectively), the microstructures are mainly composed of granular bainite (GB) and acicular ferrite (AF). The effective grain sizes are below 20 lm; the steel reached the optimal balance between the strength and the toughness; the yield strength is 695 MPa; the tensile strength is 768 MPa; the elongation is 16.6 %; the impact energy is 262 J at room temperature. All indexes could meet the requirements of X100 pipeline steel. © 2014 Shanghai University and Springer-Verlag Berlin Heidelberg.


Li C.-H.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Li C.-H.,Shanghai Special Casting Engineering Technology Research Center | He J.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Zhang Z.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | And 8 more authors.
Journal of Alloys and Compounds | Year: 2015

The carbon contamination of alloys prepared by the electro graphite crucible is impossible to avoid due to the inherit reaction between the melt and the crucible. In this study, the TiFe-based alloy is prepared by VIM process using CaO crucible as well as the electro graphite crucible. The samples are examined by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive Spectrometer (EDS), and the PCT curves are also measured. It is resulted that, the oxygen content of alloys melted by CaO crucible is almost equal to the one melted by graphite crucible and without the carbon contamination, meanwhile the carbon content of alloys obtained by the electro graphite crucible is 1860 ppm, which exceeds the tolerance of the commercial alloy (1000 ppm). The microstructure of the alloy melted by CaO crucible is dendrite, while it is composed of the equiaxed crystal with the lamellar structure and the spherical TiC particles distributed along grain boundaries or within the grain when melted by the graphite crucible; the interfacial reaction of the electro graphite crucible with TiFe alloy melt is serious and the interaction layer is formed up to 200 μm in thickness, the carbon in TiFe-based alloys forms TiC. The hydrogen desorption plateau pressure of alloys melted by CaO crucible is (0.11-0.4) × 105Pa, and that by the graphite crucible is (0.6-1) × 105Pa. This may imply that the CaO crucible may be the promising candidate for melting the high performance TiFe based hydrogen storage alloys. © 2014 Elsevier B.V. All rights reserved.


He J.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wei C.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wang S.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Meng D.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | And 6 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2016

Recently, much attention has been paid to the refractory used for the directional solidification process of TiAl intermetallics, the Y2O3 crucible/Y2O3 coated moulds seem to be the suitable candidate. However, the use of Y2O3 is limited by its low thermal shock resistance and high cost. In this work, a novel BaZrO3 refractory was introduced to the directional solidification of TiAl intermetallics. The melt of this alloy contained in BaZrO3 crucibles were heated for 30 minutes at 1600, 1650, 1700 °C, respectively, then cooled within the crucible for the investigation of the interface between the melt and the refractory. The scanning electron microscopy (SEM) was used to evaluate the surface topography and microstructure of the samples, and the energy dispersive spectroscopy (EDS) was used to analyse the chemical composition of the samples. The results indicated that no interfacial interaction layer and no obvious element diffusion were observed between the crucible and the metal, which may imply that the BaZrO3 is a promising candidate of refractory for the directional solidification of TiAl alloys. This work can provide a basis for the further study of directional solidification of TiAl alloys by using BaZrO3 shell mould.


Chen G.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Cheng Z.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wang S.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Qin Z.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | And 4 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2016

Titanium alloy was melted in a BaZrO3 crucible by an induction melting process. The microstructure of BaZrO3 refractory and the mutual dissolution after melted at different time were analyzed by optical microscopy, scanning electron microscopy, X-ray diffraction and atomic emission spectrometry, respectively. The interfacial reaction between titanium melt and BaZrO3 refractory and the dissolve behavior of BaZrO3 at different time were investigated. The results show that the thickness of BaZrO3 refractory permeable layer is approximately 20 μm after melting a low-titanium content alloy. The oxygen content reduces and the zirconium content does not change when BaZrO3 refractory contacts with the time, indicating that the BaZrO3 refractory does not react with titanium melt. Meanwhile, the thickness of BaZrO3 refractory erosion layer is approximately 2000 μm after melting a high-titanium content alloy. The oxygen and zirconium contents increase with increasing the contact time, showing that the BaZrO3 refractory reacts with titanium melt and BaO appears during the melting process. © 2016, Editorial Department of Journal of the Chinese Ceramic Society. All right reserved.


Guo Y.L.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Zhao H.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Tang L.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wang Y.J.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | And 2 more authors.
Materials Science Forum | Year: 2015

Monolithic zirconia-molybdenum (m-ZrO2/Mo) cermets have been prepared by traditional powder metallurgy process with molybdenum volume concentration of 30% and different molybdenum powders with average particle sizes of 80nm, 3μm, 8μm and 13μm. The influence of metal particle size on the morphology and electrical conductivity of the cermet has been investigated. The electrical resistivity of the cermet was measured via 4-probe DC technique from 500 ˚C to 1600 ˚C. All the samples showed the positive temperature coefficient of electrical resistivity, but the sample prepared with 80 nm molybdenum powder showed very high resistivity over 0.5 Ω·cm. Hot-press sintering was proved to be helpful to the elongated conductive phase formation, thus the electrical conductivity of cermet increased compared to the pressureless sintering process. © (2015) Trans Tech Publications, Switzerland.


Guo Y.-L.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Tang L.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Zhao H.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | Wang Y.-J.,Shanghai Key Laboratory of Modem Metallurgy and Materials Processing | And 2 more authors.
Guocheng Gongcheng Xuebao/The Chinese Journal of Process Engineering | Year: 2014

Three ceramics, pure monolithic zirconia (m-ZrO2), 3%(mol) Y2O3 doped partially stabilized zirconia (3Y-PSZ) and 12%(mol) CeO2 doped PSZ (12Ce-PSZ), were chosen for preparing three cermets by adding 30%(ψ) Mo. The relative density of the cermets was over 95%. Their static corrosion tests were conducted in a tube furnace at 1600°C for 4 h in molten IF steel and Al2O3-CaO-MgO slag respectively, and their corrosion behaviors observed. The results show that the cermet with pure m-ZrO2 has better corrosion resistance to liquid steel while the cermet with 3Y-PSZ has better corrosion resistance to molten slag. The corrosion of cermet by liquid steel is mainly involved with formation of intermetallic compounds between Fe and Mo, and the corrosion of cermet by molten slag mainly with the reaction of ZrO2 and CaO in slag for formation of CaZrO3.


Li C.H.,State Key Laboratory of Advanced Special Steel | Li C.H.,Shanghai Special Casting engineering technology research Center | He J.,State Key Laboratory of Advanced Special Steel | Wei C.,State Key Laboratory of Advanced Special Steel | And 4 more authors.
Materials Science Forum | Year: 2015

The investment casting technology is one of the major methods to produce the parts of the titanium due to its low production cost. However, the high activity of titanium melt gives rise to the requirement of high chemical stability of shell materials, to avoid or decrease the interfacial reaction between the mould and the melt. In this paper, a novel BaZrO3 – coated Al2O3 shell-mould was first introduced to the investment casting of titanium alloy. The grain size and baking temperature on the properties of the novel mould were investigated, and then the Ti6Al4V and TiNi alloys were successfully casted by means of this shell. The alloy-mould interaction was discussed. The results showed that the mould achieve high mechanical properties when the content of coarse powder was 50% after sintering 4 hours under 1500°C, and the BaZrO3 coating exhibited an effective barrier to avoid the direct contact between the mould base material and the melt, the thickness of reaction layer of TiNi alloy was about 8 µm, and 17 µm to Ti6Al4V alloy, no refractory particles and elemental diffusion were observed inside the metal. This may imply that BaZrO3 is a promising candidate material for the investment casting of titanium alloy. © (2015) Trans Tech Publications, Switzerland.


Wei Q.,State Key Laboratory of Advanced Special Steel | Li M.,State Key Laboratory of Advanced Special Steel | Chen G.,State Key Laboratory of Advanced Special Steel | Wang H.,State Key Laboratory of Advanced Special Steel | And 5 more authors.
TMS Annual Meeting | Year: 2016

The TiAl alloy with nominal composition of Ti-46Al-8Nb (at.%) is directionally solidified(DS) in a BaZrO3 coated Al2O3 mould with the certain withdrawing rates (120 μm/s), and the metal-BaZr03 interface, microstructure and chemical composition of the alloy are evaluated. The result demonstrates that after the directional solidification a fully lamellar γα2 microstructure without BaZrO3 particles contamination is observed, and the BaZrO3 protective coating exhibits an effective barrier capability to avoid the direct contact between the mould base material and the TiAl melt. The interface reaction between the mould and TiAl melt was analyzed by scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). The results showed that a certain thickness interface reaction layer is formed at the metid-mould interface with this withdrawing rate. And the reason may be the BaZrO3 coating is found to suffer some erosion and be slightly dissolved by the molten TiAl.


Lin C.,Shanghai University of Engineering Science | Wang S.,Shanghai University of Engineering Science | Chen G.,Shanghai University of Engineering Science | Wang K.,Center for Research in Computational Thermochemistry | And 5 more authors.
Ceramics International | Year: 2016

Based upon the experimental data available in the literature and present measurements, thermodynamic reassessments were initially performed on the binary BaO-ZrO2, BaO-YO1.5 systems, and the resultant thermodynamic parameters were then merged in combination with that of the previous ZrO2-YO1.5 system to derive a self-consistent thermodynamic description for the ZrO2-BaO-YO1.5 ternary system with limited ternary thermodynamic parameters. The Gibbs energies of all the liquid and terminal solid solution phases were treated by the substitutional solution model, the BZ phase featured by second solid solution described by the compound energy formalism (CEF) model, and the stoichiometric compound BZY424 and Ba2YZrO6-d modeled following the Neumann-Kopp rule. The calculated results agree well with the isothermal sections at 1600°C and 1750°C (1873K and 1923K) from both of the previous and present measured phase diagrams. This demonstrates that the thermodynamic parameters derived in the present work could be applicable to compositional optimizations of novel refractories for melting titanium alloys on the basis of this ternary oxide system. © 2016 Elsevier Ltd and Techna Group S.r.l.

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