Structural characterization and selected properties of newly-developed Al-Cr-Pd and Al-Fe-Pd alloys with structurally complex intermetallics

In this work, the structure and selected properties of newly developed Al-Cr-Pd (72 at% of Al, 24 at% of Cr, 4 at% of Pd) and Al-Fe-Pd (72 at% of Al, 24 at% of Fe, 4 at% of Pd) alloys in the form of ingots were characterized. The structure of the alloys was described on X-ray diffraction, transmission electron microscopy, and scanning electron microscopy studies. The Al-Cr-Pd and Al-Fe-Pd alloys were examined for thermal properties (differential thermal analysis), corrosion resistance (electrochemical and scanning Kelvin probe force microscopy studies), and mechanical properties (Vickers hardness and wear resistance). Both alloys were characterized by a multiphase structure with the structurally complex intermetallics. The presence of decagonal electron diffraction (D-AlPdCr) for the Al-Cr-Pd alloy was confirmed by transmission electron microscopy. The Al-Cr-Pd alloy showed a higher tendency to passivate than the Al-Fe-Pd alloy in the 3.5 % NaCl solution environment. However, the oxide layer on Al-Cr-Pd was discontinuous and less protective against further corrosion progression, as indicated by the higher corrosion current density for this alloy. For both alloys, a high contrast of Volta potentials was identified between the phases with and without palladium, which may favour the formation of galvanic microcells. The Al-Fe-Pd alloy showed a higher average hardness and a greater resistance to wear than the Al-Cr-Pd alloy.