Microstructure Formation and Nanoindentation Behavior of Rapidly Solidified Cu-Fe-Zr Immiscible Alloys

The binary Cu-Fe system is characterized by a metastable liquid miscibility gap. WhenZr is added into the Cu-Fe alloy, the miscibility gap can be extended into Cu-Fe-Zr ternary system. In the present study Cu-Fe-Zr alloys were prepared by single-roller melting-spinning method, and the samples were characterized by the SEM, EDS, HRTEM and nanoidentation. The results show that liquid-liquid phase separation into CuZr-rich and FeZr-rich liquids takes place during rapid cooling the Cu-Fe-Zr alloy, and the mechanism depends on the atomic ratio of Cu to Fe. With increasing Zr content, the size of secondary phase formed by the liquid-liquid phase separation reduces to nanoscale. The structure with amorphous Cu-rich nanoparticles embedded in the amorphous Fe-rich matrix was obtained in the as-quenched Cu20Fe20Zr60 alloy. For its structure particularity of the Cu20Fe20Zr60 sample, mechanical evaluation was carried out by using nanoindentation.

Thermodynamic Re-Assessment of the Mn-La Binary System

In this work, eleven Mn-La alloys were investigated experimentally by means of thermal analysis. The temperatures of the invariant reactions in the Mn-La binary system were determined. To confirm whether the liquid miscibility gap exists in the Mn-La system, one key alloy (Mn72La28) was prepared and then checked by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Microstructure observation and composition analysis indicated the nonexistence of the liquid miscibility gap. Based on the experimental results obtained in the present work and the critical review of the available experimental data in the published literature, a set of self-consistent thermodynamic parameters for the Mn-La system was obtained using the CALPHAD method by thermodynamic optimization of the selected experimental data.

Onset of convection in two layers of a binary liquid

We perform linear stability calculations for horizontal bilayers of a two-component fluid that can undergo a phase transformation, taking into account both buoyancy effects and thermocapillary effects in the presence of a vertical temperature gradient. Critical values for the applied temperature difference across the system that is necessary to produce instability are obtained by a linear stability analysis, using both numerical computations and small wavenumber approximations. Thermophysical properties are taken from the aluminum–indium monotectic system, which includes a liquid–liquid miscibility gap. In addition to buoyant and thermocapillary modes of instability, we find an oscillatory phase-change instability due to the combined effects of solute diffusion and fluid flow that persists at small wavenumbers. This mode is sensitive to the ratio of the layer depths, and for certain layer depths can occur for heating from either above or below.