Effects of Cr addition on the mechanical and corrosion properties of the AlMoNbTi high-entropy alloy

This study evaluates the effects of equimolar Cr addition on the mechanical and corrosion properties of the AlMoNbTi high-entropy alloy (HEA). Microstructure analysis revealed an increase in segregation by the addition of Cr in the already segregated AlMoNbTi HEA. This segregation resulted in significant hardness variations from nanoindentation tests: 9.97 to 14.41 GPa for the base AlMoNbTi HEA, and 7.92 to 14.32 GPa for the Cr-containing alloy. While AlMoNbTi exhibited a normal hardness distribution with a single peak at 12.25 GPa, AlCrMoNbTi exhibited a bimodal distribution with peaks at 9.25 GPa and 12.25 GPa. This indicates localized softening and results in a 11.68% decrease in average hardness value by the addition of Cr. To evaluate the corrosion properties, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were performed in a 3.5 wt% NaCl solution at room temperature. The results showed a 4.5% increase in charge transfer resistance and a 44.2% decrease in corrosion current due to Cr addition. The results indicate improved corrosion resistance with the addition of Cr to the AlMoNbTi HEA, at the cost of increased segregation and reduced hardness.