Corrosion and galvanic coupling of heat treated Ti-6Al-4V alloy weldment

Corrosion behavior and galvanic coupling of Ti-6Al-4V alloy weldment with various postweld heat treatments have been investigated in Ringer's solution. For this purpose, Gas Tungsten Arc Welding (GTAW) was used for butt welding of specimens. The corrosion behavior of weld metal (WM), base metal (BM) and base/weld metal coupling was compared. Finally, postweld heat treatment (PWHT) was performed to improve the corrosion behavior of Ti-6Al-4V alloy weldment. Results indicated that corrosion behavior of BM was better than WM. Furthermore, as-welded sample showed the worst galvanic coupling effect in Ringer's solution. This phenomenon was attributed to alloying elements heterogeneity due to columnar-grain microstructure of WM. PWHT, particularly solution treatment and aging improved the corrosion behavior of the weldment and decreased the corrosion rate of the galvanic coupling. Uniformity in corrosion potentials of different zones resulted from the solution treatment and aging operation carried out subsequent to welding. This was due to the precipitation of α phase and β phase from the small quantities of retained β and martensite in WM.