Effect of heat treatment on corrosion behavior of Ti–6Al–4V alloy weldments

In this study, the effect of preweld and postweld heat treatment on the corrosion behavior of Ti–6Al–4V alloy weldment was investigated. Gas tungsten arc welding (GTAW) was used for butt welding of specimens. In order to study the effects of heat treatment on the weldment microstructure and corrosion properties, a combination of stress relieving, solution treatment and aging were used. Corrosion behavior was determined in Ringer's solution at 37 °C using tafel polarization. Microstructure of base metal (BM), fusion zone (FZ) and heat affected zone (HAZ) was studied with optical and scanning electron microscopy (SEM). The results of corrosion tests showed that corrosion behavior of the BM was better than the FZ and HAZ. This phenomenon was attributed to alloying elements heterogeneity due to columnar-grain of the FZ and adjacent HAZ. Postweld heat treatment particularly solution treatment and aging improved the corrosion behavior of the weldments. Furthermore, uniformity in corrosion potentials of different zones was achieved from the solution treatment and aging operation carried out subsequent to welding. This is due to the precipitation of α-phase from the small quantities of retained β and β-phase from the martensite, respectively. Heat treatment did not have any significant effect in improving the corrosion behavior of the BM.