On the thermodynamic stability of intermetallic phases in the AA6111 aluminum alloy

An experimental investigation of both as-cast and heat-treated AA6111 alloys pointed to the quaternary phase Al₁₆(Fe,Mn)₄Si₃ as the dominant intermetallic phase. Weight fractions of this phase were determined by extracting it from the alloys via a selective dissolution of the FCC matrix in boiling phenol. The fractions found were significantly greater than those predicted by thermodynamic modeling. In an attempt to resolve the contradiction, it was assumed that the thermodynamic stability of the quaternary phase reported in literature had been underestimated. In order to refine its thermodynamic characteristics, conditions of phase equilibria in which Al₁₆(Fe,Mn)₄Si₃ participated were handled within the framework of the CALPHAD method.     

Effect of electrolysis superheat degree on anticorrosion performance of 5 Cu/（10NiO-NiFe2O4） cermet inert anode

5Cu/(10NiO-NiFe2O4) cermet inert anodes were prepared by cold-pressing and sintering process, and the effect of superheat degree of melting K3AlF6-Na3AlF6-AlF3 on their anticorrosion performance was studied under electrolysis conditions. The results show that, the fluctuation of cell becomes small with increasing of superheat degree, which is helpful to inhibit the formation of cathodic encrustation; the concentration of impurities from inert anode in bath goes up to certain degree, but it is far smaller than those in traditional high-temperature bath. Increasing the superheat degree of melting K3AlF6-Na3AlF6-AlF3 has unconspicuous effect on the contents of impurities in cathodic aluminum. The total mass fractions of Fe, Ni and Cu in aluminum are 15.38% and 15.09% respectively under superheat degree of 95 and 195 ℃. From micro-topography of anode used view, increasing the superheat degree can aggravate corrosion of metal Cu in inert anode, and has negative influence on electrical conductivity of electrode to some extent.     

Phase equilibria of the Al2O3–CaO–SiO2-(0%, 5%, 10%) MgO slag system for non-metallic inclusions control

Al₂O₃–CaO-(MgO–SiO₂) inclusions are one of the dominant inclusions in Al-deoxidized spring steel, the compositions changes of which are closely related to refining slags and deoxidization process. The Al₂O₃–CaO–SiO₂–MgO system can represent the primary ingredients of the Al₂O₃–CaO inclusions. According to analyzed compositions and predicted liquidus temperature ranges of inclusions and refining slag, equilibra experiments under high temperature, water quenching technique and subsquent electron probe X-ray microanalysis (EPMA) has been conducted to ascertain detailed thermodynamic database for inclusions control. Liquidus temperatures within the dominant phase fields of Ca₃SiO₅, Ca₂SiO₄, CaAl₂O₄, Ca₃Al₄O₉, spinel and MgO with the intervals of 20 °C from 1350 to 1560°C were identified. To further promote inclusions control, the influences of mass ratios of Mass(Al2O3)Mass(Al2O3+SiO2+CaO) and MgO contents on equilibrated phases and liquidus temperature changes have been explored. To further enhance modification levels of Al₂O₃–CaO-(MgO–SiO₂) system inclusions, it is suggested that refining time could be suitably prolonged.     

碳含量对缺碳硬质合金组织和性能的影响

通过配制不同碳含量的WC-6Co缺碳硬质合金,采用X射线衍射、光学金相、显微硬度、钴磁和TRS等分析方法,对比研究碳含量对低压烧结缺碳硬质合金的显微组织和性能的影响。结果表明:碳含量影响合金中η相的类型、含量、分布、WC的形状以及合金的性能;Co3W3C相出现在缺碳程度相对较小的合金中,其含量随碳含量的增加而增大,而Co6W6C相与之相反;合金中的η相总量随碳含量的增大而减少;随着缺碳程度的增加,合金中η相的分散均匀性变差,并且η相趋向于成大块状;WC大多呈现多角特征;合金的密度和维氏硬度随着碳含量的增加,先大幅度增加后缓慢减小,碳含量为5.2%(质量分数)时均出现最大值,合金的钴磁和横向断裂强度随着碳含量的增加而增加。     

Improved electric insulation ability and ferromagnetic property in Nb2O5 doped BiFeO3-based multiferroic ceramics

Journal of Electroceramics - 0.675BiFeO3-0.3BaTiO3-0.025LaFeO3-x mol% Nb2O5 (x?=?0–1.25) multiferroic lead- free ceramics, fabricated by conventional solid-state reaction, were...     

Numerical optimization for blades of Intermig impeller in solid–liquid stirred tank

The multiphase flow in the solid-liquid tank stirred with a new structure of Intermig impeller was analyzed by computational fluid dynamics(CFD).The Eulerian multiphase model and standard k-ε turbulence model were adopted to simulate the fluid flow,turbulent kinetic energy distribution,mixing performance and power consumption in a stirred tank.The simulation results were also verified by the water model experiments,and good agreement was achieved.The solid-liquid mixing performances of Intermig impeller with different blade structures were compared in detail.The results show that the improved Intermig impeller not only enhances the solid mixing and suspension,but also saves more than 20% power compared with the standard one.The inner blades have relatively little influence on power and the best angle of inner blades is 45°,while the outer blades affect greatly the power consumption and the optimized value is 45°.     

Effect of high temperature on the mechanical properties of hierarchical porous cenosphere/geopolymer composite foams

A hierarchical porous cenosphere/geopolymer composite foam (FHCs/KGP) was fabricated by the simultaneous incorporation of O₂ pore from hydrogen peroxide and cenosphere filler addition. Effects of both H₂O₂ content and high-temperature treatment on the microstructure, porosity and strength of porous FHCs/KGP foams were investigated systematically. The obtained FHCs/KGP foams showed typical amorphous structure and desirable porosity from 65 to 82%. The composites could crystallize in situ to FHCs/leucite foams above 1000℃. Compression strength of the FHCs/leucite foams showed a maximum value of 5 ± 0.3 MPa when treated at 1000°C. The improvement of mechanical properties for the composite foams was attributed to crack deflection, fractured microspheres and the good bond between the FHCs and matrix. This study could open opportunities to employ cellular foams as alternatives in structure and filtration applications.