Papers by Keyword: Multi-Component Alloys

Abstract: Tracer diffusion is one of most reliable techniques for providing basic kinetic data in solids. In the present review, selected direct methods, in particular the radiotracer measurements as a superior technique due to its high sensitivity, Secondary-Ion-Mass-Spectroscopy (SIMS) profiling, X-Ray Diffraction measurements and Rutherford Backscattering Spectrometry are presented and discussed. Special attention is put on the radiotracer technique describing the currently used sectioning techniques in detail with a focus on the experimental applications and complications. The relevant experimental results are exemplary shown. Furthermore, the most recent developments and advances related to the combined tracer/inter-diffusion measurements are highlighted. It is shown that this approach offers possibilities to provide the concentration-dependent tracer diffusion coefficients of the constituting elements in multi-component alloys in high-throughput experiments. Possibilities of estimating the tracer diffusion coefficients following different types of diffusion couple methods in binary and multicomponent systems are briefly introduced. Finally, specificity of SIMS analysis of diffusion in fine-grained materials are carefully analyzed. If applicable, a direct comparison of the results obtained by different techniques is given.

Abstract: Five multi-component alloy (MCA) formulations of CoFeMnNiZn (MCA01), Al_0.5CoFeMnNiZn (MCA02), Al_1.0CoFeMnNiZn (MCA03), Co₅Fe₅Mn₃₀Ni₂₀Zn₄₀ (MCA04) and Al_8.4Co_4.6Fe_4.6Mn₂₇Ni_18.4Zn₃₇ (MCA05) were prepared by mechanical alloying and melting process (MAM). Five-component alloys of MCA01-MCA05 were designed using empirical formulae for high entropy alloys. Phase formation and microstructure were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that MCA01 was partially melted by MAM process. However, MCA02-MCA05 could be melted and cast by MAM process. The microstructures of as-cast MCA02 and MCA03 showed dendritic solidification. Nevertheless, the as-cast MCA04 showed microstructure similar to that of Ni-based superalloy, i.e., the as-cast MCA04 consisted of γ matrix and γ′ phase. Moreover, egg type core shell structure was found in the interdendritic regions of the MCA05 alloy. In addition, the Al-added MCA02 and MCA03 alloys showed crystal structures of FCC1, FCC2 and BCC. MCA04 alloy demonstrated crystal structure of FCC whereas MCA05 alloy had crystal structures of FCC and Primitive Cubic.

Abstract: The solution redistribution was an important phenomenon during the solidification of multi-component alloys. The improvements of the solute redistribution were considered in this paper especial in the simulation processes. The models of Gibbs free energy were taken into three kinds such as pure materials, the substitutional solution and the sublattice. Calculating the Gibbs free energy of the system, the solute redistribution coefficients could be calculated. The simulated results of Al-Cu binary and Al-Si-Mg ternary alloys agree well with the experimental results.

Abstract: A method to estimate the thermodynamic properties of Multi- component white gold alloys from those of constitutive binary alloys was proposed. The Miedema's theory and Chou model. were used to calculate the formation enthalpies of Au–Cu–Ni-Zn-RE alloys. The agreement between the calculation and experiment is reasonable. Formation enthalpies of Au–Cu–Ni-Zn-RE and relative stability of their intermetallic compounds were predicted with present method.

Abstract: The precipitation kinetics path in multi-component alloys may involve a competition between atomic mobilities and precipitates thermodynamic stability. Cluster dynamics modelling (CDM) is a simulation method that allows to describe this competition without introducing any heuristic assumptions as, for example, in the classical theory of nucleation. CDM consists in solving numerically, for each time increment, the master equations expressing the balance of solute exchanges (absorption and emission) between clusters/precipitates. A key issue is the energetics of the nano-clusters in the nucleation range. The computation of the precipitate size distribution function allows the complete description of the precipitates kinetic evolution, in chemical composition and in size. The method is applied to the precipitation of the Al3(Zr,Sc) L12 phase in Al solid solutions. The model predicts fairly well in the precipitation path some observed coupling effects between the two solutes, particularly during the nucleation stage.