Microstructure, Phase Occurrence, and Corrosion Behavior of As-Solidified and As-Annealed Al-Pd Alloys
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In the present work, we studied the microstructure, phase constitution, and corrosion performance of Al88Pd12, Al77Pd23, Al72Pd28, and Al67Pd33 alloys (metal concentrations are given in at.%). The alloys were prepared by repeated arc melting of Al and Pd granules in argon atmosphere. The as-solidified samples were further annealed at 700 °C for 500 h. The microstructure and phase constitution of the as-solidified and as-annealed alloys were studied by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. The alloys were found to consist of (Al), ε n (~ Al3Pd), and δ (Al3Pd2) in various fractions. The corrosion testing of the alloys was performed in aqueous NaCl (0.6 M) using a standard 3-electrode cell monitored by potentiostat. The corrosion current densities and corrosion potentials were determined by Tafel extrapolation. The corrosion potentials of the alloys were found between − 763 and − 841 mV versus Ag/AgCl. An active alloy dissolution has been observed, and it has been found that (Al) was excavated, whereas Al in ε n was de-alloyed. The effects of bulk chemical composition, phase occurrence and microstructure on the corrosion behavior are evaluated. The local nobilities of ε n and δ are discussed. Finally, the conclusions about the alloy’s corrosion resistance in saline solutions are provided.
KeywordsAl-Pd alloys corrosion resistance intermetallic microstructure characterization potentiodynamic polarization
The authors wish to thank the European Regional Development Fund (ERDF) for financial support of the project ITMS:26220120048 “Center for Development and Application of Advanced Diagnostic Methods in Processing of Metallic and Non-metallic Materials” funded within the Research & Development Operational Programme, the Grant Agency VEGA for the financial support under contracts 1/0018/15 and 1/0465/15, and the Slovak Research and Development Agency for the financial support under the contract APVV-15-0049.
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