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Selection of raw materials and control of trace elements for production of high-quality SG iron

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China Foundry 2019年第2期16卷 79-87页

作者： Jia-xin bai China University of Geoscience Beijing

During the production of SG iron, the selection of raw materials and control of chemical composition are most important. From the very early days of SG iron production, the effects of trace elements on graphite form and matrix structure have been studied, and the allowable concentration limits for their detrimental influence has been decreased year by year, during the last fifty years. This paper has reviewed some of the suggested SG iron trace elements in the literature and in several Chinese foundries. It was found that for most SG iron castings, rare earth elements are still required to neutralize the harmful effects of trace elements and improve SG iron quality. It also found that the use of high purity and ultra-high purity base iron melts enabled integrated, safety-critical and complicated SG iron castings of varying thickness, and heavy-section, to be produced successfully. These SG iron castings have surprisingly good structures, and their mechanical and dynamic properties are vastly superior to those specified in current international SG iron standards. Further study is required on the effects of using high purity and ultra-high purity base melts on the structure and properties of SG iron.

关键词： trace elements anti-nodulizing and pearlite factors chunky graphite high and ultra-high purity pig iron high quality SG iron

Effect of Cu content on the glass forming ability of Cu-Zr-Ti system studied by ion beam mixing

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Science China(Technological Sciences) 2015年第4期58卷 750-752页

作者： WANG Yuan Yu WANG Qi LIU bai xin Key Laboratory of Advanced Materials (MOE) School of Materials Science and Engineering Tsinghua University

Based on the Cu-Zr-Ti ternary phase diagram,four sets of Cu-Zr-Ti multilayered films with various compositions of Cu20Zr36Ti44,Cu36Zr31Ti33,Cu49Zr24Ti27,and Cu67Zr16Ti17 were prepared and then the ion beam mixing was carried *** turned out that the increase of Cu content doesn't always have a positive effect on the glass forming *** glass forming ability of Cu49Zr24Ti27 was degraded due to the appearance of a Cs Cl-type B2 structure Cu Zr phase in the eutectic *** experimental observations justify the existence of the Cu Zr phase under the non-equilibrium *** formation mechanisms for the crystalline phase were also discussed in terms of the atomic collision theory.

关键词： glass forming ability ion beam mixing films

Ablation-resistant Ir/Re coating on C/C composites at ultra-high temperatures

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Rare Metals 2022年第1期41卷 199-208页

作者： Hong Zhang Li-An Zhu Shu-xin bai Yi-Cong Ye Department of Materials Science and Engineering College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China

An iridium/rhenium(Ir/Re)double-layer coating was prepared on carbon/carbon(C/C)composites by chemical vapor deposition(CVD)and *** morphologies and bond strengths of the coatings on the C/C substrate were *** ablation resistance of the Ir/Re coating was studied at 1800℃in an oxyacetylene torch flame for 300 *** results show that Re interlayer increases the bond strength between Ir coating and C/C substrate by over 100%.During entire hightemperature ablation process,Ir/Re coating keeps intact without any signs of ablation *** coating gets smoother and the grain size becomes larger after ablation,with the preferred orientation changing from h311i to h220i:Although some voids are observed along the grain boundaries of the as-ablated Ir coating,Ir/Re coating keeps intact on C/C *** study indicates that Ir/Re coating can provide good ablation resistance up to 1800℃for C/C composites,especially for the continuous ablation applications.

关键词： Iridium Rhenium Carbon/carbon(C/C) Interlayer Ablation

Synthesize of Metallic Glasses in Immiscible Mo-Cu System by Ion Mixing of Multilayers

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Chinese Physics Letters 1997年第3期14卷 194-197页

作者： CHEN Yi-gang LIU bai-xin Department of Materials Science and Engineering Tsinghua UniversityBeijing 100084 State Key Laboratory of Solid-state Microstructures Physics Nanjing UniversityNanjing 210093

In the properly designed Mo-Cu multilayered films by free energy concern,several new metallic glasses,were obtained by ion mixing in an immiscible Mo-Cu *** elucidate the unexpected glass formation,a Gibbs free energy diagram was constructed on the basis of Miedema’s model,with a special consideration to include the interfacial free energy into the initial state of the multilayered *** turned out that the interfacial free energy raised the multilayered films to an energetic state higher than that of the amorphous phase in a specific range depending on the fraction of interfacial atoms and that the ion-induced glass transition observed in this system was generated by the interfaces.

关键词： interfacial glass glasses

Experimental and Theoretical Studies on Composition Limits of Metallic Glass Formation in the Ni-Mo System

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Chinese Physics Letters 1999年第9期16卷 667-669页

作者： LI Zheng-cao LIU bai-xin Department of Materials Science and Engineering Tsinghua UniversityBeijing 100084

The Ni-Mo system was selected as a model system to study the composition limits of metallic glass formation by ion mixing experiments as well as by molecular dynamics simulation. The 200keV xenon ion mixing was conducted for ten Ni-Mo mutilayered samples with various concentrations and the results showed that the glass-forming composition range was 39.8-80.4at.% Mo, which is in good agreement with the assessment from an empirical model. Through comparing the stability of the Ni-rich and Mo-rich solid solutions with various concentrations versus their amorphous counterparts, two critical supersaturated solid solubilities were found by molecular dynamics simulation to be 21 at.% Mo in Ni and 25at.% Ni in Mo, from which the glass forming range was deduced to be within 21-75 at.% Mo. The correlation of the simulated glass-forming range with those obtained by ion irradiation and solid-state reaction is also discussed.

关键词： glass mixing solid

Enhancement of Atomic Rearrangement in Top Surface Layers by Low Energy Ions

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Chinese Physics Letters 1998年第9期15卷 671-673页

作者： MA Zhong-quan LIU bai-xin Functional Materials Laboratory Department of PhysicsXinjiang UniversityUrumqi 830046 Department of Materials Science and Engineering Tsinghua UniversityBeijing 100084

Assuming rectilinear trajectories for the projectile into a solid surface,a specific expression for the“energy window”of the driving atoms in a monolayer has been derived for different ion-target systems,in which the atomic displacements occur primarily in the surface layer,while the subsurface layer is kept *** results obtained here are in good agreement with Brice et al.’s numerical estimations and close to experimental data for ion beam assisted depositions.

关键词： monolayer primarily layer

Synergistic effect of palladium and oxygen vacancies in the Pd/perovskite catalysts synthesized by the spc method

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Journal of Environmental Sciences 2005年第1期17卷 19-24页

作者： ZHOUKe-bin CHENHong-de TIANQun ZHUBao-wei SHENDi-xin XUXiao-bai ResearchCenterforEco-EnvironmentalSciences ChineseAcademyofSciencesBeijing100085China

A series of oxygen deficient perovskite supported palladium catalysts were prepared by the “solid phase crystallization'(spc) method and investigated with XRD, TPR, TPD, TEM, XPS, BET analysis and CO oxidation. It was found that Pd/perovskite catalysts synthesized by the spc method were more active for CO oxidation than the calcined LaCo 0 95 Pd 0 05 O 3, where Pd dispersed in the solid solution. H 2 reducing treatment in the spc method could yield not only high dispersed fine Pd particles on the perovskite surface but also oxygen deficient structure. In these perovskite supported Pd catalysts, oxygen vacancies adsorbed, activated and supplied oxygen to the active Pd sites, where the oxidation occurred with adsorbed CO. The high activities were due to the cooperative action of Pd and oxygen vacancies.

关键词： Pd perovskite oxygen vacancies adsorbed oxygen spc method CO oxidation

Microstructure and Mechanical Properties of Al_(2)O_(3p)/AZ91 Magnesium Matrix Laminated Material Adjusted by Freezing Temperature

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Acta Metallurgica Sinica(English Letters) 2024年第11期37卷 1819-1829页

作者： Ze-xin bai Kun-Kun Deng Ze-Qi Du Kai-Bo Nie Chao Xu Quan-xin Shi Shanxi Key Laboratory of Advanced Magnesium-based Materials College of Materials Science and EngineeringTaiyuan University of TechnologyTaiyuan 030024China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

The Al_(2)O_(3)laminated preforms with different layers thickness were prepared by freezing casting in present ***,the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 alloy melt into the Al_(2)O_(3)laminated preform based on pressure infiltration ***,the influence of freezing temperature on the microstructure,mechanical properties and fracture behavior of magnesium-based laminates was *** results indicated that with the decrease of freezing temperature,the thickness of Al_(2)O_(3)layers decreases gradually,the number of layers increases obviously,and the interlayers spacing *** with the decrease of interlayers spacing,the size of Mg17Al12 phase precipitated in the AZ91 alloy layers was refined,and the compression strength and strain were both improved *** micro-cracks initiated in Al_(2)O_(3)layers during loading process,while the AZ91 layers could effectively suppress the initiation and propagation of ***,the changing layers structure influenced by the decrease of freezing temperature had significant inhibiting effect on the initiation and propagation of micro-cracks,which endowed the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials with better strength and ***,the best compression properties of Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials could be obtained at the freezing temperature of−50℃,the compression strength and elastic modulus of which were the 160%and 250%of monolithic AZ91 alloy,respectively.

关键词： Bio-inspired composites Freeze-casting Mechanical properties Metal matrix composites

A comparative study of rhenium coatings prepared on graphite wafers by chemical vapor deposition and electrodeposition in molten salts

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Rare Metals 2021年第1期40卷 202-211页

作者： Jiang-Fan Wang Shu-xin bai Yi-Cong Ye Li-An Zhu Hong Zhang College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China

The purity,preferred orientation,microstructure,microhardness,bonding strength,thickness uniformity and thermal stability of rhenium(Re)coatings prepared on graphite wafers by chemical vapor deposition(CVD)and electrodeposition(ED)in molten salts were comparatively studied in this *** was found that carbon(0.0140 wt%)and oxygen(0.0067 wt%)were the primary impurities for CVD and ED Re coatings,*** diffusion of carbon into CVD Re coating caused higher microhardness near the substrate and helped to improve the bonding strength at the same *** preferred orientation,microstructure and microhardness of ED Re coating were all susceptible to *** coating deposition uniformity of ED Re is obviously better than that of CVD Re coating,due to its intrinsic ***(002)-oriented,coarse columnar CVD Re coating exhibited better thermal stability compared with that of the-oriented,fiber-like columnar ED Re coating,while the ED Re grains grew remarkably and the microstructure evolved toward the similar structure of CVD Re after annealing *** diversity of Re coatings in microstructure could be attributed to the mobility of grain boundaries(affected by temperature and impurity)during deposition processes.

关键词： Rhenium coating Graphite wafer Chemical vapor deposition Electrodeposition Molten salt Grain boundary mobility