Characterization and kinetic modeling of secondary phases in squeeze cast Al alloy A380 by DSC thermal analysis

Thermal analyses on squeeze cast aluminum alloy A380(SC A380) solidified under 90MPa were carried out to study the microstructure development of the alloy, in which a differential scanning calorimeter(DSC) was employed. During the DSC runs, heating and cooling rates of 1, 3, 10, and 20 °C·min^(-1) were applied to investigate the heating and cooling effects on dissolution of secondary eutectic phases and microstructure evolution. Various reactions corresponding to troughs and peaks of the DSC curves were identified as corresponding to phase transformations taking place during dissolution or precipitation suggested by the principles of thermodynamics and kinetics. The comparison of the identified characteristic temperatures in the measured heating and cooling curves are generally in good agreement with the computed equilibrium temperatures. The microstructure analyses by scanning electron microscopy(SEM) with energy dispersive X-ray spectroscopy(EDS) indicate that the distribution and morphology of secondary phases present in the microstructure of the annealed sample are similar to the as-cast A380, i.e., strip β(Si), buck bone like or dot distributed θ(Al_2Cu), β(Al_5Fe Si) and Al_(15)(FeMn)_3Si_2. Two kinetic methods are employed to calculate the activation energies of the three common troughs and three common peaks in DSC curves of SC A380. The activation energies of the identified reaction θ_(CuAl_2) = α(Al)+β(Si) is 188.7 and 187.1 k J?mol^(-1) when the activation energies of reaction α(Al)+β(Si)→θCu Al_2 is^(-1)22.7 and^(-1)21.8 k J?mol^(-1), by the Kissinger and Starink methods, respectively.

The stationary phase analysis of the Kirchhoff-type d emigrated field

In the literature,stationary phase analysis of Kirchhoff-type demigrated fields is carried out mainly under the following two conditions：（1） The considered isochrone and the target reflector are tangential to each other;（2） The spatial duration of the wavelet of the depthmigrated image is short.For the isochrones that are not tangential to the target reflector and for the depth-migrated images that have a large spatial duration,the published stationary phase equation for the demigrated field will become invalid.For performing the stationary phase analysis of the Kirchhoff-type demigrated field under the conditions that the considered isochrone and the target reflector are not tangential to each other and that the spatial duration of the wavelet of the depth-migrated image is not short（the general conditions）,I derive the formulas for the factors appearing in the stationary phase formula in two dimensions,from which I find that for different isochrones the horizontal coordinates of the stationary point of the depth difference function are different.Also,the equation for the Kirchhoff-type demigrated field consists of two parts.One is the true-amplitude demigrated signal and the other is the amplitude distortion factor.From these facts the following two conclusions can be drawn：（1） A demigrated signal is composed of many depth-migrated images and one depth-migrated image trace provides only one sample to the demigrated signal;and（2） The amplitude distortion effect is an effect inherent in the Kirchhoff-type demigration and cannot be eliminated during demigration.If this effect should be eliminated,one should do an amplitude correction after demigration.

MULTI-PEAK MATCH INTENSITY RATIO METHOD OF QUANTI-TATIVE X-RAY DIFFRACTION PHASE ANALYSIS

A new method for quantitative phase analysis is proposed by using X-ray diffraction multi-peak match intensity ratio. This method can obtain the multi-peak match intensity ratio among each phase in the mixture sample by using all diffraction peak data in the mixture sample X-ray diffraction spectrum and combining the relative intensity distribution data of each phase standard peak in JCPDS card to carry on the least square method regression analysis. It is benefit to improve the precision of quantitative phase analysis that the given single line ratio which is usually adopted is taken the place of the multi-peak match intensity ratio and is used in X-ray diffraction quantitative phase analysis of the mixture sample. By analyzing four-group mixture sample, adopting multi-peak match intensity ratio and X-ray diffraction quantitative phase analysis principle of combining the adiabatic and matrix flushing method, it is tested that the experimental results are identical with theory.

AN EXTERNAL STANDARD METHOD OF QUANTITATIVE PHASE ANALYSIS OF THE SAMPLE CONTAINING AN AMORPHOUS PHASE BY X—RAY DIFFRACTION

A new method of the quantitative phase analysis of the sample containing an amorphous phase or a standardless phase by X-ray diffraction is proposed in the paper. The addtion of a reference phase or some analytical phase to the analyzed sample is not required in this method and the experimental results are satisfactory.

Symplectic analysis for elastic wave propagation in two-dimensional cellular structures

On the basis of the finite element analysis, the elastic wave propagation in cellular structures is investigated using the symplectic algorithm. The variation principle is first applied to obtain the dual variables and the wave propagation problem is then transformed into two-dimensional （2D） symplectic eigenvalue problems, where the extended Wittrick-Williams algorithm is used to ensure that no phase propagation eigenvalues are missed during computation. Three typical cellular structures, square, triangle and hexagon, are introduced to illustrate the unique feature of the symplectic algorithm in higher-frequency calculation, which is due to the conserved properties of the structure-preserving symplectic algorithm. On the basis of the dispersion relations and phase constant surface analysis, the band structure is shown to be insensitive to the material type at lower frequencies, however, much more related at higher frequencies. This paper also demonstrates how the boundary conditions adopted in the finite element modeling process and the structures＇ configurations affect the band structures. The hexagonal cells are demonstrated to be more efficient for sound insulation at higher frequencies, while the triangular cells are preferred at lower frequencies. No complete band gaps are observed for the square cells with fixed-end boundary conditions. The analysis of phase constant surfaces guides the design of 2D cellular structures where waves at certain frequencies do not propagate in specified directions. The findings from the present study will provide invaluable guidelines for the future application of cellular structures in sound insulation.

A phase analysis of vorticity vectors associated with tropical convection

Three new vorticity vectors have been proposed by Gao et al to study the two-dimensional tropical convection. In the present paper, phase relations between surface rain rate and the vorticity vectors are analysed with the calculations of lag correlation coefficients based on hourly zonally-averaged mass-integrated cloud-resolving simulation data. The cloud-resolving model is integrated with the vertical velocity, zonal wind, horizontal thermal and moisture advections, and sea surface temperature observed and derived from tropical ocean global atmosphere - coupled ocean atmosphere response experiment （TOGA-COARE） for 10 days. Maximum local increase of the vertical component of the convective vorticity vector leads maximum surface rain rate by 2 hours mainly due to the interaction between vorticity and zonal gradient of ice heating. While maximum local increase of the vertical component of the moist vorticity vector leads maxfinum surface rain rate by 2 hours mainly because of the interaction between zonal specific humidity gradient and zonal buoyancy gradient. And the maximum local decrease of the zonal component of the dynamic vorticity vector leads maximum surface rain rate by 2 hours mainly due to the interactions between vorticity and vertical pressure gradient as well as vorticity and buoyancy.

In situ synthesis and phase analysis of low density O'-sialon-based multiphase ceramics

In situ formed low density O＇-sialon-based multiphase ceramics were prepared by liquid-phase sintering method at 1400°C with Si3N4, SiO2 and Al2O3 as raw materials.Crystalline phases were identified by X-ray diffraction（XRD）.The quantitative phase analysis was finished by matrix-flushing method and the substitution parameter x value of O＇-sialon was estimated.The effects of sintering additives on the phase composition of the material were studied.The results show that, when using Y2O3 alone, Al6Si2O13 phase can be formed in the material, but when using Y2O3 and MgO, MgAl2O4 phase can be preferentially formed and the Al6Si2O13 is not observed.The mechanical properties of the material were measured and the relationships between microstructure and mechanical properties were discussed.The sample with Y2O3 and MgO sintering additives, using fused quartz alone as SiO2 source, displays a combination of high bending strength（163 MPa） and good fracture toughness（3.11 MPa·m1/2）.Bending strength and fracture toughness of the samples increase with the increase of the content and aspect ratio of elongated grains and decrease with the increase of the porosity.

Stress-Induced Precipitation of Fineγ'-Phase and Thermodynamics Analysis

The microstructures of a single crystal Ni-base superalloy with [001] orientation were observed by means of TEM. Results showed that the fine γ' particles were precipitated in the γ matrix channels during the tensile deformation of the alloy. Thermodynamics analysis indicated that the solubility of elements M(Al,Ta) within the γ matrix may be changed when the alloy was deformed by the external applied stress. The tensile stress reduced the solubility of elements Al and Ta so as to occur the over-saturation and agglomeration of them, which promoted the precipitation of fine γ'-phase in the γ matrix.

AN INCREMENTAL METHOD OF X-RAY DIFFRACTION QUANTITATIVE PHASE ANALYSIS OF SAMPLESCONTAINING AMORPHOUS MATERIAL

A new method for quantitative X-ray diffraction phase analysis of a powder misture has been developed according to Popovic's doping method. The weight fraction of amorphous material in the analysed sample is obtained. For a multicomponent system in which (n-2) pure phases are added into an n-phase compnent sample and theweight fractions of all n phases can be determined by the method. The test results of confirmation agree well with the theory.

Potentiostatic Etching and Etching Quantitative Analysis of Carbides in Die Steel

The differential etching methods of carbides M_6C, MC and M_(23)C_6 in die steel havebeen studies by volt-ampere method and potentioastatic method. It can be used for the observation ,identification and quantitative analysis of carbides.

Analysis of Rare-Earth Phase in a W-Mo-Ni-Fe-Mn-La Heavy Alloy

Besides W-phase and Ni-phase, there is a micro new phase in W-Mo-Ni-Fe heavy alloy added with La and Mn. The micro phase can he extracted as an electrolytic residue by the following method: A mixture of the new phase and the Ni-phase is isolated when an alloy sample is electrolyzed in 5%NaOH+1% tartaric acid solution. And the new phase can be isolated alone when the mixture is electrolyzed in 10% acetylacetone +1%LiCl methanol solution. The result of the quantitative phase analysis indicates that the new phase is a complex oxide rich in La, W and Mn.The interfacial segregation of oxygen decreases and the binding force between W-Ni Phases increases because of the existence of the oxide. So the mechanical properties of the alloy are improved.

A SOLUTION OF MINIMUM NORM FOR QUANTITATIVE PHASE ANALYSIS BY STANDARDLESS X-RAY DIFFRACTION

A new expression of quantitative phase analysis by standardless X-ray diffraction has been derived using intensity matrix of vector modulus.The criterion of standardless X-ray diffraction analysis was suggested,so as to separate the diffraction pattern of every phase from that of sample.The optimal solution could be obtained by the least squares regression.

A SOLUTION OF MINIMUM NORM FOR QUANTITATIVE PHASE ANALYSIS BY STANDARDLESS X-RAY DIFFRACTION

A new expression of quantitative phase analysis by standardless X-ray diffraction has been derived using intensity matrix of vector modulus,The criterion of standardless X-ray diffraction analysis was suggested,so as to separate the diffraction pattern of every phase from that of sample.The optimal solution could be obtained by the least squares regression.

Application of Potentiostats Using PC in the Phase Analysis of Galvano-Chemis-try

A set of device is designed based on PC to realize the functions of traditional potentiostats in the phase ana1ysis of galvanochemistry. In the device, A/D and D/A conversion is used to measure the electrode potential and convert the voltage for outPut; specific program runs in the PC to regulate and control the system. The effect of the proportion factor Kp on the control variation is researched through certain experiment. Two experiments, the control of electrolysis in constant poteniial and the determination of polarization curves, are designed to test and evaluate the effectiveness of the device. The experimemel results show that the variation between the actualanode potential and the target potential could be controlled to below 1 mV if Kp is set to an appropriate value.

Phase analysis of Al metal in complex deoxidizer

Complex deoxidizer is an important supplementary material for steelmaking,which can not only absorb liquid steel inclusions and improve the quality of molten steel,but also enhance deoxidation,desulfurization, dephosphorization,to prevent the molten steel suction and reduce the molten steel temperature loss.Currently,the complex deoxidizer all contain a certain amount of metal aluminium.The metal aluminium can not be determined for the steel.The entire aluminium contents were regarded as the content of approximate metal aluminium,that often bring great economic losses.Because A1,0,price is cheaper than metal aluminite powder,suppliers added a certain amount of Al_2O_3 in complex deoxidizer,pretend to be the metal aluminium to reap huge profits.This paper put forward a kind of method for determining aluminum,which would reduce loss of the enterprise.Research and put forward an iron triehloride,which extracted from Al metal from complex deoxidizer.Meantime,using orthogonal design of the experiment has been optimized for working conditions.The RSD of the samples are I. 07%-1.94%,the recoveries of the experiment results are 97.0%-110.0%,which expressed the precision and accuracy of the experiment are good.The establishment of the iron triehloride as a extractor,which is rapid and accurate for determination of Al metal in complex deoxidizer.

Preliminary study on washability and composition analysis of high- sulfur coal in some mining areas in Guizhou

Preliminary sink-float experiments on high-sulfur coal was done in some mining areas and carried on elementary analysis, industrial analysis, and ashcontent analysis. Through the experiments, definite middlings, and gangue, the phase analysis of sulfur was carried on, by which a good understanding of sulfur characters in raw coal was achieved.

A DFB Fiber Laser Sensor System with Ultra-High Resolution and Its Noise Analysis

A distributed feedback fiber laser （DFB FL） sensor system with ultra-high resolution is described. The sensor is made by writing distributed feedback structures into a high gain active fiber, and the system employs an unbalanced Michelson interferometer to translate laser wavelength shifts induced by weak measurands into phase shifts. A digital phase generated carrier demodulation scheme is introduced to achieve ultra-high resolution interrogation. A detailed noise analysis of the system is presented, and it is shown that the system resolution is limited by the frequency noise of the DFB FL.

Beam Steering Analysis in Optically Phased Vertical Cavity Surface Emitting Laser Array

Beam steering in implant defined coherently coupled vertical cavity surface emitting laser （VCSEL） arrays is simulated using the FDTD solution software. Angular deflection dependent on relative phase differences among elements, inter-element spacing, element size and emitted wavelength is analyzed detailedly and systematically. We design and fabricate 1×2 implant defined VCSEL arrays for optimum beam steering performance. Electroni- cally controlled beam steering with a maximum deflection angle of 1.6° is successfully achieved in the 1 × 2 VCSEL arrays. The percentage of the power in the central lobe is above 39% when steering. The results show that the steering is controllable. Compared with other beam steering methods, the fabrication process is simple and of low cost.

NON-AQUEOUS REVERSED PHASE HPLC WITH LOW-WAVELENGTH UV DETECTION FOR TRIGLYCERIDE ANALYSIS

Glycerides are first separated to classes of triglycerides(TGs), diglycerides(DGs) and monoglycerides(MGs) by normal phase HPLC on silica gel column. Individual triglyceride separation is then achieved by non-aqueous reversed phase(NARP) HPLC on C_(18) column with UV detection at 215nm.