Study synergistic effect of Ti addition on microstructure and electrochemical performance of cost-effective Co-free AlCrFeNi high-entropy alloy with dual-phase architecture

Herein, the effect of Ti addition on the microstructure and electrochemical behavior of cost-effective Co-free AlCrFe2Ni2 high-entropy alloy in a 0.5 M H2SO4 solution was investigated. Upon the introduction of Ti into the AlCrFe2Ni2 alloy, the crystal structure transitioned from face-centered cubic (FCC), body-centered cubic (BCC), and ordered body-centered cubic (B2) phases to a predominantly BCC/B2 structure in the AlCrFe2Ni2Ti0.5 alloy. Furthermore, Ti addition increased the volume fraction of the interdendritic regions, and Ti-rich intermetallic regions were formed in the interdendritic regions, resulting in significant grain refinement. In the AlCrFe2Ni2Ti0.5 alloy, this unique structure mitigates the negative influences of the dual-phase architecture and element segregation on corrosion performance, thereby promoting the formation of a more stable and thicker passive oxide film. These findings demonstrate that introducing Ti, as an excellent corrosion-resistant element, was an effective strategy for significantly improving the electrochemical behavior of cost-effective Co-free AlCrFeNi high-entropy alloys.