Fucheng Yin

Effect of Si on growth kinetics of intermetallic compounds during reaction between solid iron and molten aluminum

The effect of Si on the growth kinetics of intermetallic compounds during the reaction of solid iron and molten aluminum was investigated with a scanning electron microscope coupled with an energy dispersive X-ray spectroscope, and hot-dip aluminized experiments. The results show that the intermetallic layer is composed of major Fe2Al5 and minor FeAl3. The Al−Fe−Si ternary phase, τ1/τ9, is formed in the Fe2Al5 layer. The tongue-like morphology of the Fe2Al5 layer becomes less distinct and disappears finally as the content of Si in aluminum bath increases. Si in the bath improves the prohibiting ability to the growth of Fe2Al5 and FeAl3. When the contents of Si are 0, 0.5%, 1.0%, 1.5%, 2.0% and 3.0%, the activation energies of Fe2Al5 are evaluated to be 207, 186, 169, 168, 167 and 172 kJ/mol, respectively. The reduction of the activation energy might result from the lattice distortion caused by Si atom penetrating into the Fe2Al5 phase. When Si atom occupies the vacancy site, it blocks easy diffusion path and results in the disappearance of tongue-like morphology.

Thermodynamic assessment of the Ag-Ce (silver-cerium) system

Abstract An optimized thermodynamic description of the Ag–Ce system has been obtained from experimental thermodynamic and phase diagram data by means of the computer program THERMO-CALC based on the least-squares method, using models for the Gibbs energy of individual phases. The Ag–Ce system contains four intermetallic compounds. The calculated standard enthalpies of formation of AgCe, Ag 2 Ce, Ag 51 Ce 14 and Ag 4 Ce are −22.331, −20.194, −18.998, −17.863 kJ/mol, respectively. The calculated values and experimental data are in good agreement

Experimental investigation and thermodynamic calculation of the Zn―Al―Sb system

Abstract The 873 K isothermal section of the Zn–Al–Sb ternary system was experimentally determined using scanning electron microscopy coupled with wave and energy dispersive X-ray spectroscopy. No ternary compound was found in the present study. Based on the experiment results together with available information in the literature, the phase diagram calculation for Zn–Al–Sb was carried out by means of the CALPHAD technique. A consistent set of thermodynamic parameters for each phase was derived. The optimized results and the experimental data are in good agreement.

Experimental investigation of the Zn-Fe-V system at 450°C

Abstract Phase relations in the Zn – Co – Sb ternary system have been studied experimentally for the whole composition range, using scanning electron microscopy coupled with energy-dispersive spectrometry and X-ray diffraction. The ternary compound named CoZnSb, containing 26.0 to 36.1 at.% Co, 31.1 to 36.5 at.% Zn and 31.8 to 39.7 at.% Sb, still exists at 450 °C. Moreover, the experimental results indicate that twelve tri-phase regions could be confirmed in the system at 450 °C, and the maximum solubility of Zn in CoSb is up to 6.0at.%.

On the thermodynamic assessment of the Ag–La system

Abstract The phase diagram and thermodynamic data of the Ag–La system were critically assessed by means of the computer programs THERMO-CALC, using models for the Gibbs energies of individual phases. The system contains four intermetallic compounds. Good agreement is obtained between the calculation and experimental results.

In situ study on columnar-equiaxed transition and anaxial columnar dendrite growth of Al-15%Cu alloy by synchrotron radiography

Directional solidification of Al-15% (mass fraction) Cu alloy was investigated by in situ and real time radiography which was performed by Shanghai synchrotron radiation facility (SSRF). The imaging results reveal that columnar to equiaxed transition (CET) is provoked by external thermal disturbance. The detaching and floating of fragments of dendrite arms are the prelude of the transition when the solute boundary layer in front of the solid-liquid interface is thin. And the dendrite triangular tip is the fracture sensitive zone. When the conditions are suitable, new dendrites can sprout and grow up. This kind of dendrite has no obvious stem and is named anaxial columnar dendrites.

560°C isothermal section of the Zn-Fe-Ni-Si quaternary system at the zinc-rich corner

Abstract The 560°C isothermal section of the Zn – Fe – Ni – Si quaternary system with the Zn composition being fixed at 93 at.% has been determined using optical microscopy, scanning electronic microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray diffractometry. It was found that FeSi is in equilibrium with almost all phases in the section, including the δ-Fe – Zn, FeSi2, T (Zn – Fe – Ni ternary compound), γ-Ni – Zn, NiSi2 and liquid phases. The existence of the L + FeSi + NiSi2 + γ-Ni – Zn four-phase equilibrium prevents other Ni-Si compounds from entering equilibrium with the liquid phase at 560°C. No true quaternary compound was found in the present study.

Phase equilibria of the Al–Ni–Zn system at 340°C

Abstract The phase equilibria at 340°C of the Al – Ni – Zn system were investigated by combining the diffusion couple technique with the equilibrated alloys method. The samples were examined by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. Two ternary compounds (1 and 2) were found to exist at 340°C. The solubilities of Zn in AlNi, Al3Ni2 and Al3Ni were determined to be about 20, 2 and 1 at.% Zn, respectively. The solubilities of Al in β1-NiZn and in were measured to be about 11.5 and 1 at.% Al, respectively. The solubilities of Zn in both AlNi3 and Al3Ni5 are below 1 at.% Zn.

On thermodynamic assessment of the Ag–Pr system

Abstract Optimized descriptions of the phase diagram and thermodynamic properties of the Ag–Pr system have been obtained from experimental thermodynamic and phase diagram data by means of the computer program thermo-calc based on the least squares method, using models for the Gibbs energy of individual phases. The system contains four intermetallic compounds. The calculated standard enthalpies of formation of AgPr, Ag 2 Pr, Ag 51 Pr 14 and Ag 5 Pr are −23.580 kJ/mol, −22.132 kJ/mol, −21.246 kJ/mol and −21.393 kJ/mol, respectively. A consistent set of thermodynamic parameters was derived. Optimized and experimental data are in good agreement.

Experimental study of the phase relations in the Fe–Zn–Cr system at 600°C

Abstract The isothermal section of the Fe–Zn–Cr ternary system at 600 °C was determined using equilibrated alloys with the aid of a diffusion couple approach. The specimens were investigated by means of scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, electron probe microanalysis and X-ray diffraction. The results showed that (Cr) is in equilibrium with all phases in the system except (α-Fe). A ternary phase with an approximate formula of Fe18Zn79Cr3 was found. The composition ranges of all intermetallic phases in the system were determined. The solubility of Zn in (Cr) is about 2.5 at.%, and that of Cr in the δ, Γ and liquid zinc is 3.1, 5.4 and 1.4 at.%, respectively.