Effect of electron beam surface melting on the microstructure and corrosion behavior of Ti-4Al-4Zr-2Sn-1.5Mo-Nb-V alloy

Improving the corrosion resistance of titanium alloys is essential for their long-term performance in marine environments. This study investigates the effect of electron beam surface melting (EBSM) on the microstructure and corrosion behavior of a Ti-4Al-4Zr-2Sn-1.5Mo-Nb-V alloy. The EBSM induces the formation of a refined Widmanstätten microstructure, primarily composed of α′ martensite and residual β phase, due to the rapid solidification. Electrochemical tests indicate that the EBSM can significantly improve the corrosion resistance, and the sample processed by a beam current of 55 mA exhibits the best performance, with the smallest passivation current density (1.33 μA cm⁻²) and highest polarization resistance (0.34 MΩ cm²). This improvement induced by EBSM is attributed to the formation of a denser and more stable passive film, confirmed by a higher cation ratio (CR, defined as the ratio of Cf(Ti4++Al3++Zr4++Sn4+) to Cf(Ti3++Ti2++Ti+Al+Zr+Sn2++Sn), with values of 1.80 for the forged sample and 2.25 for the 55 mA sample) and reduced electrochemical activity. These findings highlight EBSM as a promising surface engineering strategy for advancing the durability of titanium alloys in aggressive chloride-containing environments.