Analysis of Intermetallic Particles by a Technique of Dissolution of the Al-rich matrix of an Al–Fe-Sn alloy

Referencia Apresentador Autores
Camila Yuri Negrão Konno Konno, C.Y.(Universidade Estadual de Campinas); Kakitani, R.(Universidade Estadual de Campinas); Verissimo, N.C.(Universidade Estadual de Campinas); Goulart, P.R.(Universidade Estadual de Campinas); Cheung, N.(Universidade Estadual de Campinas); Garcia, A.(Universidade Estadual de Campinas); Since the early 50´s, due the fossil fuel crisis and crescent pollution indexes, the growing demand for energy has been encouraging the research for more efficient, economic and less environmental impact renewable energy sources. Sources of energy such as wind and solar power, hydropower and biomass, are gaining attention in research for power generation. Among all those technologies, hydrogen is considered the fuel of the future, with several obtaining routes, e.g. water electrolysis. Although the concept of reaction with water for hydrogen production is not new, recent studies show that the reaction can be used to power fuel cell devices, such as emergency generators, portable computers, and for cell-powered vehicles of fuel. Aluminum and it´s alloys appear as a new and source for hydrogen production and energy storage. Among Al alloys, the Al-Fe alloy is the most prominent and stands with in terms of compatibility for such applications. Besides, the addition of alloying elements can improve such qualities. The most suitable alloying element for hydrogen production is tin (Sn), which is responsible to improve activity of Al-Fe alloys due to SnH4 formation and the breakdown of Al2O3 passive layers formed. It is well known that this process accelerates the H2 production even in weak alkaline solutions. In the present work, a non-equilibrium water-cooled unidirectional solidification process was carried out to achieve the growth of a ternary Al-1wt.%Fe-1wt.%Sn alloy casting, which is associated with a range of experimental solidification cooling rates at different positions along the length the casting. It is shown that a cellular morphology characterizes the Al-rich matrix along the entire casting, having Al-Fe intermetallics (IMCs) rods distributed along with the Sn-rich phase. Both Al6Fe and Al3Fe IMCs (rod like) are shown to be well distributed along the cellular boundaries, with a very small fraction of plate-like Al3Fe particles. Once morphology, size, distribution and chemical composition of IMCs are fundamental to the mechanical behavior of Al-based alloys, their characterization carries important information with a view to permitting correlations with the alloy properties to be established. In the present work a technique for the dissolution of the Al-rich matrix, is used to permit a more accurate characterization of IMCs to be carried out. This includes a clear evaluation of the distribution, shape and chemical composition of the fibrous IMCs using a SEM technique. Microstructural and chemical analyses on undissolved samples were also carried out by SEM and EDX. In addition, X-ray diffractograms were performed to identify Sn, Al as well as the intermetallic phases. The experimental results have permitted the different patterns of Al-Fe intermetallics and of the scale of the cellular matrix to be correlated with solidification thermal parameters such as the cooling and the growth rate.
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