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 (ₓ₈^{4++Al^3++Zr^4++Sn^4+) } to Cf (ₓ₈^{3++Ti^2++Ti+Al+Zr+Sn^2++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.