Papers by Author: Xing Jun Liu

Abstract: In this paper, by considering the irradiation-enhanced diffusion, a combination of effective free energy model and the thermodynamic model was used for studying the phase relationships in the U-Ti and U-V binary system under irradiation. The steady-state dynamical phase diagrams of U-Ti and U-V binary alloys under different irradiation intensities were calculated and compared with the conventional thermodynamic equilibrium phase diagram. The calculated results show that under irradiation the high-temperature stable (βTi, γU) and (γU,V) phases were stabilized at relatively low temperature resulting in invariant reactions at relatively low temperature. In addition, with the increase of the irradiation intensity, the temperature of the invariant reactions increased, and the phase regions of the (βTi, γU) and (γU,V) also increased.

Abstract: With available melting point and hardness, the Bi-based filler alloy is considered as one choice of high-temperature Pb-free solder. Phase diagram can play an important role in the design of new type of Pb-free solder.In the present work, the thermodynamic assessments of the Au-Nd and the Au-Lu binary systems have been carried out by the Calculation of Phase Diagram (CALPHAD) method based on the available experimental data. The Gibbs free energies of the solution phases were described by subregular solution models with the Redlich-Kister equation, and those of the intermetallic compounds were described by sublattice models. A set of self-consistent and reasonable thermodynamic parameters is obtained for the binary systems, which describes the Gibbs energies of the solution phases and the intermetallic compounds phases. Additionally, combined the reported Bi-Au, Bi-Lu and Bi-Nd binary systems, the thermodynamic database of the Bi-Au-Lu and the Bi-Au-Nd ternary systems have been developed, which will provide important thermodynamic information for the phase equilibria of the multicomponent Bi-based alloy systems.

Abstract: Sc-based alloys have been used as aero-structures materials, and Sc addition on wrought alloys has positive effects on weldability and welding properties. Phase diagrams play an effective role during the development of new type of alloy with good properties. Therefore, to establish the thermodynamic database of Sc-X binary systems is important and necessary.In the present work, the thermodynamic assessments of Sc-X (Ag, B, Cr, Er, Gd, Mo, Th, W, Y, Zr) binary systems was carried out by using CALPHAD (Calculation of Phase Diagrams) method based on the experimental data including thermodynamic properties and phase equilibria. The Gibbs free energies of the solution phases were described by the sub-regular solution model with the Redlich-Kister equation, and those of the intermetallic compounds were described by the sub-lattice model. A set of self-consistent thermodynamic parameters were derived for describing the Gibbs free energies of each solution phase and intermetallic compound. The calculated phase diagrams and thermodynamic properties are in good agreement with experimental data. The thermodynamic database of the Sc-X (Al, Ag, B, Ca, Co, Cr, Cu, Er, Fe, Ga, Gd, Ge, La, Li, Mg, Mn, Mo, Ni, Pb, Pd, Ru, Sn, Th, W, Y, Zn, Zr) binary systems have been developed, which can provide much important thermodynamic information for multicomponent Al-Sc based alloys.

Abstract: Equivalent magnetic circuit method is a rapid calculation method used in magnetic circuit simulation. But for a long time this method can’t be used widely because the algorithm is not general and there is no commercial software developed for this method. In this paper, general software for magnetic circuit calculation was developed using LabVIEW language. Quasi-Newton algorithm was used in solving nonlinear Kirchhoff equation of magnetic circuit in this software. The project file in this software can be shared freely in different calculations. This software is expected to save the time-cost in the design of new product.

Abstract: The evolutions of microstructure and phase transformation behavior of Cu-Al-Fe-Nb/Ta high-temperature shape memory alloys under the quenched and aged states were investigated in this study, including Cu-10wt.% Al-6wt.% Fe, Cu-10wt.% Al-4wt.% Fe-2wt.% Nb and Cu-10wt.% Al-4wt.% Fe-2wt.% Ta three types alloys. The obtained results show that after quenching, Cu-10wt.% Al-6wt.% Fe alloy exhibits two-phase microstructure of β′₁ martensite + Fe (Al,Cu) phase; Cu-10wt.% Al-4wt.% Fe-2wt.% Nb alloy also has two-phase microstructure of (β′₁ + γ^′₁ martensites) + Nb (Fe,Al,Cu)₂ phase; Cu-10wt.% Al-4wt.% Fe-2wt.% Ta alloy is consisted of three-phase of (β′₁ + γ^′₁ martensites) + Fe (Al,Cu,Ta) + Ta₂(Al,Cu,Fe)₃ phases. However, α (Cu) phase precipitates after aging for three alloys; and Fe (Al,Cu,Nb) phase is also present in Cu-10wt.% Al-4wt.% Fe-2wt.% Nb alloy. All the studied alloys exhibit complicated martensitic transformation behaviors resulted from the existence of two types martensites (β′₁ and γ^′₁).

Abstract: New Cu–Fe-based ternary systems have been developed to fabricate monolithic porous materials through electrochemical dealloying process in a 1.84 mol/L H2SO4 solution. The microstructures of the porous materials were characterized using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The results show that the compositions of the as-melt Cu-Fe-Co and Cu-Fe-Ni alloys have an important effect on the electrochemical dealloying process and microstructures of the monolithic porous materials.

Abstract: The microstructure and phase transformation behavior of Ni-Mn-Fe high-temperature shape memory alloys including Ni_40+xFe₁₀Mn_50-x (x = 0, 10) were investigated. The results show that both two alloys exhibit single fcc γ phase annealed at 900°C for 1 day. When these quenched alloys are again annealed at 500°C for 20 days, they almost exhibit main tetragonal θ martensite. The microstructural evolutions are consistent with the results of phase transformation measurements. It is clearly found that there is an irreversible phase transformation around 480°C ~ 570°C, which is associated with the formation of tetragonal θ martensite from γ phase. Afterwards, the reversible martensitic transformation occurs during heating and cooling with very high transformation temperature.

Abstract: The Cu/Ni, Ni/Cu and Cu/Ni/Si film/substrate and film/film/substrate systems were prepared by magnetron sputtering method to investigate the surface segregation. The chemical composition of film was analyzed by Auger Electron Spectroscopy (AES). The microtopographies of the Cu/Ni surface and the cross section of the film were observed by Transmission Electron Microscope (TEM), where the blocky distribution of Ni-rich area on surface of Cu film and columnar grains was observed in the specimen. It is found that the thickness of sputtered film has stronger effect on the composition of segregation layer near the surface than that of the annealing time. The surface segregation could be ascribed to the fast vertical diffusion of the substrate atoms through the columnar grain boundaries and the subsequent lateral surface diffusion.

Abstract: To investigate the mechanism of self-bias magnetoelectric effect in magnetoelectric composite materials, a synchronous characterization technique was developed to characterize the magnetoelectric effect, the magnetostrictive effect, and the magnetic hysteresis loop by one-time test. The results of a magnetoelectric composite consisting of hybrid ferromagnetic phases showed that the obvious magnetoelectric hysteresis behavior was found with significant self-bias magnetoelectric effect. In addition, after demagnetizing, the residual magnetic polarization became zero and the magnetoelectric effect disappeared at the same time. Since the ferromagnetic phases were separated from each other, the mechanism of self-bias magnetoelectric effect mainly resulted from static magnetic coupling instead of build-in magnetic field. It was concluded that the synchronous characterizing technique was quite helpful when analyzing the mechanism of magnetoelectric behavior.

Abstract: The effects of Nb addition on microstructures, Young’s moduli, tensile properties of Ti-30Ta-xNb (x = 21, 24, 27, 30, wt. %) alloys were investigated in this study. The results show that dual phases containing β phase and a little α" martensite were observed when x = 21 and 24, whereas single β phase is present when x = 27 and 30. A minimum Young’s modulus of 52.13 GPa was obtained in Ti-30Ta-21Nb alloy. Ti-30Ta-xNb alloys exhibit high strength-to-modulus ratios, showing their great potentials to develop as new candidates for biomedical applications.