Two stages of immiscible liquid separation in the formation of Panzhihua-type Fe-Ti-V oxide deposits,SW China

Magmatic oxide deposits in the～260 Ma Emeishan Large Igneous Province（ELIP）,SW China and northern Vietnam,are important sources of Fe,Ti and V.Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua,Hongge,and Baima deposits,are well described in the literature and are hosted in layered mafic-ultramafic intrusions in the Panxi region,the central ELIP.The same type of ELIP- related deposits also occur far to the south and include the Anyi deposit,about 130 km south of Panzhihua,and the Mianhuadi deposit in the Red River fault zone.The Anyi deposit is relatively small but is similarly hosted in a layered mafic intrusion.The Mianhuadi deposit has a zircon U-Pb age of～260 Ma and is thus contemporaneous with the ELIP.This deposit was variably metamorphosed during the Indosinian orogeny and Red River faulting.Compositionally,magnetite of the Mianhuadi deposit contains smaller amounts of Ti and V than that of the other deposits,possibly attributable to the later metamorphism.The distribution of the oxide ore deposits is not related to the domal structure of the ELIP.One major feature of all the oxide deposits in the ELIP is the spatial association of oxide-bearing gabbroic intrusions,syenitic plutons and high-Ti flood basalts.Thus,we propose that magmas from a mantle plume were emplaced into a shallow magma chamber where they were evolved into a field of liquid immiscibility to form two silicate liquids,one with an extremely Fe-Ti-rich gabbroic composition and the other syenitic.An immiscible Fe-Ti-（P） oxide melt may then separate from the mafic magmas to form oxide deposits.The parental magmas from which these deposits formed were likely Fe-Ti-rich picritic in composition and were derived from enriched asthenospheric mantle at a greater depth than the magmas that produced sulfide-bearing intrusions of the ELIP.

Reflection and refraction of attenuated waves at boundary of elastic solid and porous solid saturated with two immiscible viscous fluids

The propagation of elastic waves is studied in a porous solid saturated with two immiscible viscous fluids. The propagation of three longitudinal waves is represented through three scalar potential functions. The lone transverse wave is presented by a vector potential function. The displacements of particles in different phases of the aggregate are defined in terms of these potential functions. It is shown that there exist three longitudinal waves and one transverse wave. The phenomena of reflection and refraction due to longitudinal and transverse waves at a plane interface between an elastic solid half-space and a porous solid half-space saturated with two immiscible viscous fluids are investigated. For the presence of viscosity in pore-fluids, the waves refracted to the porous medium attenuate in the direction normal to the interface. The ratios of the amplitudes of the reflected and refracted waves to that of the incident wave are calculated as a non- singular system of linear algebraic equations. These amplitude ratios are used to further calculate the shares of different scattered waves in the energy of the incident wave. The modulus of the amplitude and the energy ratios with the angle of incidence are computed for a particular numerical model. The conservation of the energy across the interface is verified. The effects of variations in non-wet saturation of pores and frequencies on the energy partition are depicted graphically and discussed,

Calculation of Activity Coefficient from Immiscible Binary Alloy Phase Diagram by Means of Modified Sub-regular Solution Model

The modified sub regular solution model was used for a calculation of the activity coefficient of immiscible binary alloy systems. The parameters needed for the calculation are the interaction parameters, λ 1 and λ 2, which are represented as a linear function of temperature, T . The molar excess Gibbs free energy, G m E, can be written in the form G m E= x A x B[( λ 11 + λ 12 T )+( λ 21 + λ 22 T ) x B ] The calculation is carried out numerically for three immiscible binary alloy systems, Al Pb, Cu Tl and In V. The agreement between the calculated and experimentally determined values of activity coefficient is excellent.

Mechanical Alloying of Ag-Cu Immiscible Alloy System

Mechanical alloying has been performed in Ag-Cu immiscible alloy system with five different compositions. X-ray diffraction analysis was carried out to determine the structural characterization of the milled powders. Lattice constants of the milled powders were determined and the solubility for Ag in Cu was calculated. The results demonstrated that MA indeed produced a face center cubic (f.c.c.). Cu-based Cu-Ag solid solution and the solid solubility has been extended to x(Ag)=30% for Ag in Cu when the grain size of Cu-based Cu-Ag solid solution is about 10 nm after MA. There is a three-phases co-existence during the process of MA in this alloy system which agrees well with other experimental and theoretical results. Based on the experimental results a formation model was proposed in this paper to understand the formation of Ag-Cu solid solution during MA.

A FINITE ELEMENT COLLOCATION METHOD FOR TWO-PHASE INCOMPRESSIBLE IMMISCIBLE PROBLEMS

Two-phase, incompressible, immiscible flow in porous media is governed by a coupled system of nonlinear partial differential equations. The pressure equation is elliptic, whereas the concentration equation is parabolic, and both are treated by the collocation scheme. Existence and uniqueness of solutions of the algorithm are proved. A optimal convergence analysis is given for the method.

Magnetohydrodynamics instability of interfacial waves between two immiscible incompressible cylindrical fluids

The problem of nonlinear instability of interfacial waves between two immiscible conducting cylindrical fluids of a weak Oldroyd 3-constant kind is studied. The system is assumed to be influenced by an axial magnetic field, where the effect of surface tension is taken into account. The analysis, based on the method of multiple scale in both space and time, includes the linear as well as the nonlinear effects. This scheme leads to imposing of two levels of the solvability conditions, which are used to construct like-nonlinear Schr6dinger equations （1-NLS） with complex coefficients. These equations generally describe the competition between nonlinearity and dispersion. The stability criteria are theoret- ically discussed and thereby stability diagrams are obtained for different sets of physical parameters. Proceeding to the nonlinear step of the problem, the results show the appearance of dual role of some physical parameters. Moreover, these effects depend on the wave kind, short or long, except for the ordinary viscosity parameter. The effect of the field on the system stability depends on the existence of viscosity and differs in the linear case of the problem from the nonlinear one. There is an obvious difference between the effect of the three Oldroyd constants on the system stability. New instability regions in the parameter space, which appear due to nonlinear effects, are shown.

Mathematical model of micropolar fluid in two-phase immiscible fluid flow through porous channel

This paper is concerned with the flow of two immiscible fluids through a porous horizontal channel. The fluid in the upper region is the micropolar fluid/the Eringen fluid, and the fluid in the lower region is the Newtonian viscous fluid. The flow is driven by a constant pressure gradient. The presence of micropolar fluids introduces additional rotational parameters. Also, the porous material considered in both regions has two different permeabilities. A direct method is used to obtain the analytical solu- tion of the concerned problem. In the present problem, the effects of the couple stress, the micropolarity parameter, the viscosity ratio, and the permeability on the velocity profile and the microrotational velocity are discussed. It is found that all the physical parameters play an important role in controlling the translational velocity profile and the microrotational velocity. In addition, numerical values of the different flow parameters are computed. The effects of the different flow parameters on the flow rate and the wall shear stress are also discussed graphically.

Effect of high magnetic field on solidification microstructure evolution of a Cu-Fe immiscible alloy

The liquid phase separation behavior and the evolution of the solidification microstructure of a binary Cu_(50)Fe_(50) alloy were investigated under the conditions of without and with a 10 T magnetic field,with different undercooling during the solidification process.Results show that the combined effect of Stokes motion and Marangoni convection leads to the formation of the core-shell structure under the condition without the magnetic field.In addition,specific gravity segregation is reinforced by increasing the undercooling,resulting in Fe-rich phase drifts towards the sample edge.In the 10 T magnetic field,the Fe-rich phase is elongated in the parallel direction of the magnetic field under the action of demagnetization energy due to the difference of static magnetic energy and surface energy.In the vertical direction,through the action of Lorentz force,the convection in the melt is inhibited and Fe-rich phase becomes more dispersed.Meanwhile,the diffusion of the two phases and the coagulation of the Fe-rich phases are also restrained under the magnetic field,therefore,the phase volume fraction of the Fe-rich phase decreases at the same undercooling in the 10 T magnetic field.The magnetic field inhibits the segregation behavior in the vertical direction of the magnetic field,and at the same time,improves the gravitational segregation to a certain extent,which has a very important impact on microstructure regulation.

Model for calculation of microstructural development in rapidly directionally solidified immiscible alloys

A model has been developed for the calculation of the microstructural evolution in a rapidly directionally solidified immiscible alloy. Numerical solutions have been performed for Al Pb immiscible alloys. The results demonstrate that at a higher solidification velocity a constitutional supercooling region appears in front of the solid/liquid interface and the liquid liquid decomposition takes place in this region. A higher solidification velocity leads to a higher nucleation rate and, therefore, a higher number density of the minority phase droplets. As a result, the average radius of droplets in the melt at the solid/liquid interface decreases with the solidification velocity.

Simulation of nucleation and coalescence of second phase droplets during earth-based solidification process of immiscible alloys

The solidified microstructure of immiscible alloys strongly depends on the nucleation, diffusional growth, especially the coalescence of the second phase droplets in the miscibility gap. A numerical model based on the discrete multi-particle approach was developed to simulate the nucleation and coalescence mode of the second phase droplets during the earth-based processing of immiscible alloys (in this case, the effect of gravity cannot be neglected). The cooling rate is the major factor influencing the coalescence mode. Under the super-rapid or rapid solidification condition (>104K/s), Brownian collision is the dominant coalescence mode. Marangoni collision becomes the dominant mode under the sub-rapid solidification condition (>102K/s). In the conventional slow cooling scope(101K/s), Stokes collision becomes the dominant coalescence mode, correspondingly, leading to a serious phase segregation.

Large-Scale Segregation of Immiscible Liquids in the 1780 Ma Taihang Dykes to Produce the Bimodal Xiong'er Volcanics(North China)

It is yet unclear whether large-scale segregation of immiscibile liquids and eruption of high-Si lavas exist in nature(Charlier et al.,2013).We present a possible case of segregation of immscible liquids in the 1780 Ma Taihang

Microstructure evolution of immiscible alloys during rapid cooling through miscibility gap

A numerical model was developed to describe the coarsening of the second phase droplets under the common action of nucleation, diffusional growth and Brownian collision between minority phase droplets during rapidly cooling a hypermonotectic alloy through its miscibility gap. The simulated results show that Brownian motion is an important factor influencing the coarsening process. A faster cooling rate leads the supersaturation of the matrix liquid and the nucleation rate to grow up to a higher level, but leads to a smaller droplet radius and a higher number density. This model is used to predict the microstructural evolution of melt spun Al 30%In ribbon. The model reflects the real physical processes well and is expected to be applicable to other immiscible alloys or other preparing processes.

A NEW NUMERICAL METHOD FOR TWO-PHASE IMMISCIBLE INCOMPRESSIBLE PROBLEM

Two-phase, immiscible, incompressible flow in porous media is governed by a system of nonlinear partial differential equations. In most practical applications convection physically dominates diffusion, and the object of this paper is to develop a finite difference method combined with the method of characteristics and the lumped mass method to treat the parabolic equation of the differential system. This method is shown satisfy the maximum principle and its error analysis is presented.

Microstructural Features of Spray-Deposited Immiscible Bearing Alloys Al-43Sn and Al-7Sn-1.3Cu-1.3Ni

Two commercial grade aluminum based immiscible bearing alloys were spray-deposited using convergent-divergent type of nozzle. The processing parameters for spray-deposition were adjusted in such a way that most of the droplets arrived on the deposition substrate in either liquid or semi-liquid state. The microstructural features of spray-formed and as-cast alloys are compared. In spray-formed alloys equiaxed grains were observed. The cell boundaries and intercellular regions were observed to be decorated with sub-micron sized particles whereas in normal casting the second phase was observed to be segregated along grain boundaries. The morphology and distribution of second phase were observed to have similarity with those in over-spread and atomized powders produced under similar processing conditions. The microstructural features observed with variation in spray conditions are discussed in detail.

Unsteady mixed convective heat transfer of two immiscible fluids confined between long vertical wavy wall and parallel flat wall

The combined effects of thermal and mass convection of viscous incom- pressible and immiscible fluids through a vertical wavy wall and a smooth flat wall are analyzed. The dimensionless governing equations are perturbed into a mean part （the zeroth-order） and a perturbed part （the first-order）. The first-order quantities are ob- tained by the perturbation series expansion for short wavelength, in which the terms of the exponential order arise. The analytical expressions for the zeroth-order, the first-order, and the total solutions are obtained. The numerical computations are presented graph- ically to show the salient features of the fluid flow and the heat transfer characteristics. Separate solutions are matched at the interface by using suitable matching conditions. The shear stress and the Nusselt number are also analyzed for variations of the governing parameters. It is observed that the Grashof number, the viscosity ratio, the width ratio, and the conductivity ratio promote the velocity parallel to the flow direction. A reversal effect is observed for the velocity perpendicular to the flow direction.

THREE DIMENSIONAL SIMULATION OF UNSTABLE IMMISCIBLEDISPLACEMENT IN THE POROUS MEDIUM

In this study changes of uncontinuous potential functions at the interface were used to simulate the immiscible displacement in porous media. The elliptic partial differential equation was changed to a seven-point molecule form algebraic equation in three dimensions using the finite difference method. The strongly implicit procedure was adopted to determine the potential functions at every tone instant. Then the change of interface was determined. The simulation was continued until the displacement changed to unstable state. The effect of capillary pressure, wetting property, and nonuniformity of permeability were considered.

Formation Mechanism of Microstructure of Melt Spun Al-In Immiscible Alloys

Immiscible alloys are attractive for their valuable physical and mechanical properties. In this paper, Al-ln immiscible alloy is prepared by melt spinning process and its morphological evolution is studied at various indium contents. The results show that the morphologies of the matrix phase depend on the indium content. Different morphologies lead to different distribution of the second phase particles. Due to a particular solidification mechanism of immiscible alloys, even under the melt spinning rapid solidification condition, it is still impossible to produce homogeneous Al-ln hypomonotectic alloy ribbons. But for Al-ln hypermonotectic alloys, there is almost no segregation of the second phase throughout the cross section of the ribbons.

Numerical simulation of the Liquid-liquid phase separation and microstructure evolution of Al-In immiscible alloys during cooling

A numerical model has been developed to describe the microstructural evolution of Al In immiscible alloys through the miscibility gap. The model considers the common action of nucleation, diffusible growth, Brownian collision and motion collision between the second phase droplets. The simulation results are dynamically visualized and show that the volume fraction, distribution and size of the second phase droplets satisfactorily agree with the experimental results. So the model can be used to predict the microstructural evolution of Al In immiscible alloys during the cooling process.

Effect of Processing Parameters on Microstructures of Melt-Spun Al-In Immiscible Alloys

Melt spinning rapid solidification technique was employed to fabricate homogeneous Al-ln immiscible alloys and their final microstructures and morphologies were investigated. There existed a transition of columnar Al grain-equiaxed grain for the thicker ribbon, but only columnar Al grain for the thinner ribbon throughout the thickness. In the columnar grain field, most of the fine In particles was distributed within the cells, but a minority of bigger In particles or short rods was perpendicularly distributed at the grain boundaries. In the equiaxed grain field, the fine In particles were located in Al grains and coarser particles were situated at the boundaries. The average particle size increased with increasing distance from the chilled surface throughout the ribbon. At the same wheel speed (same cooling rate), the average particle size increased with raising In content. At the same composition condition, the average particle size decreased with increasing wheel speed and/or decreasing ejection temperature.