Manuel V. Canté

Primary dendrite arm spacing during transient directional solidification of Al alloys with low redistribution coefficients

Particular analytical expressions based on a curve fitting on numerical results for primary dendritic growth have been proposed in the literature to encompass binary alloy systems whose redistribution coefficient (k 0) approaches zero. To date, these expressions have not been checked against experimental results of transient solidification. The present study developed a comparative analysis between the theoretical predictions furnished by such expressions and results from transient solidification experiments with low k 0 aluminum alloys. The analysis has shown that the proposed approach generally describes the primary dendritic spacing during solidification of Al–Sn alloys which are characterized by very low k 0 values as well as by very large solidification ranges.

Electrochemical Behavior of an Al-Fe-Ni Alloy Affected by Nano-Sized Intermetallic Particles

The aim of this study is to determine the effect of the resulting microstructural array of an as-cast Al-1 wt% Fe-1 wt% Ni alloy on its electrochemical corrosion behavior in a stagnant and naturally aerated 0.5 M NaCl solution at room temperature. Electrochemical impedance spectroscopy (EIS) plots, potentio-dynamic polarization curves, and equivalent circuits are used to evaluate the corrosion response. It was found that nano-sized Al9FeNi intermetallic (IMC) particles have an important role on the corrosion resistance, which significantly affect the anode/cathode area ratio and as consequence, the examined electrochemical parameters. A mixture of interconnected spheroids and fiber-like IMC particles induces a drastic and rapid increase in the current density, while intermittent IMC particles reduce the corrosion action.

SEM Characterization of Al3Ni Intermetallics and its Influence on Mechanical Properties of Directionally Solidified Hypoeutectic Al-Ni Alloys

Rod-like Al3Ni intermetallic structures have been widely studied by Bridgman techniques of solidification. However, there is a lack of experiments conducted under unsteady-state solidification conditions. Such conditions are very close to the industrial reality since the thermal solidification variables (tip cooling rate, tip growth rate and thermal gradient) are freely changing as solidification progresses. In this research, Al3Ni structures found in hypoeutectic Al-Ni alloys were characterized under transient solidification conditions. Two Al-Ni alloys (1.0 and 5.0 wt%Ni) were directionally solidified. SEM (Scanning Electron Microscope) micrographs were obtained along the casting length (P). It was possible to observe with adequate magnifications the distribution of rod-like Al3Ni particles along the interdendritic regions. In order to emphasize the examination of morphology and distribution of such particles, the aluminum-rich matrix was dissolved by immersion of the sample in a fluoride acid solution (0.5%HF + 99.5% H2O). The effects of nickel content, dendritic arrangement and Al3Ni distribution on mechanical properties were investigated by tensile tests.

Numerical and experimental analysis of rapidly solidified laser remelted Al 5wt pct Ni surfaces

The aim of this work was to develop a heat transfer mathematical model based on the finite difference method in order to simulate temperature fields in the laser surface remelting process. Convective heat transfer in the remelted pool was taken into account by using the effective thermal conductivity approach. Theoretical predictions furnished by previous models from the literature were used for validation of numerical simulations performed with the proposed model. Experiments of laser surface remelting of Al-5 wt pct Ni samples were carried out in the present investigation, and numerical simulations were applied for the laser machine operating parameters. The work also encompasses an analysis of microstructural and microhardness variations throughout the resulting treated and untreated zones.