Abstract
High entropy alloys: AlCrFe2Ni2Mox (x = 0.00, 0.05, 0.10, 0.15), AlCoCrFeNi and two quinary alloys with compositions close to its face centered cubic (FCC) and body centered cubic (BCC) component phases, are tested for corrosion resistance in 3.5 wt. % NaCl. The materials with different microstructure produced by arc melting or ingot metallurgy are evaluated by several electrochemical techniques: measurements of open circuit voltage (OCV), cyclic potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Microstructure, surface topography and composition are systematically characterized by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The results indicate that minor additions of Mo positively affects corrosion resistance of the AlCrFe2Ni2 alloy by hampering pit formation. The FCC phase in the equimolar alloy, AlCoCrFeNi, is proved to exhibit more noble corrosion potential and pitting potential, lower corrosion current density, and corrosion rate compared with the BCC phase. Overall behavior of the investigated alloys is influenced by the manufacturing conditions, exact chemical composition, distribution of phases and occurrence of physical defects on the surface.
Highlights
The notion of high-entropy alloys (HEAs) or more generally high-entropy materials was coined quite recently and immediately awoke enormous interest by providing pathways for the development of new materials or improvement of the existing ones
Phase fractions in the as-cast alloy AlCrFe2Ni2 + 1.9 at.% Mo determined by image analysis (Figures 2A,B) on several scanning electron microscope (SEM)-BSE images were the following in area %: FCC(A1) 55.9 ± 1.3, BCC(B2) 35.5 ± 2.1, and BCC(A2) 8.5 ± 2.0
Electrochemical measurements in 3.5 wt% NaCl allowed formulation of the following conclusions regarding corrosion behavior of the investigated high-entropy alloys: (1) Microstructure of the AlCrFe2Ni2 alloys determined by the manufacturing and processing conditions influenced their chemical behavior to some extent
Summary
The notion of high-entropy alloys (HEAs) or more generally high-entropy materials was coined quite recently and immediately awoke enormous interest by providing pathways for the development of new materials or improvement of the existing ones. The multi-principal element alloys are referred to as HEAs or compositionally complex alloys even when their configurational entropy is not high enough to secure stability of a single solid solution. Second phases are formed, including either solid solutions or intermetallics or both, which are accompanied by strong segregation of alloying elements (Pickering and Jones, 2016). That is, ductility and strength, of a number of single-phase HEAs did not meet basic requirements for structural applications, major developments were switched toward the design and fabrication of dual phase FCC + BCC alloys. One of the promising results of this work was AlCoCrFeNi2.1, a castable eutectic high-entropy alloy with very good combination of high fracture strength and ductility (Lu et al., Corrosion of Al(Co)CrFeNi Alloys
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