Effect of Heat Treatment on Electrochemical Behavior of Additively Manufactured Ti-6Al-4 V Alloy in Ringer’s Solution

Titanium and its alloys are widely used as implant materials due to their exceptional biocompatibility, light weight, good mechanical properties and high corrosion resistance. Despite remarkable corrosion resistance of titanium alloys, loosening of implants occurs after long-term use due to metallic ions produced during corrosion. This work focuses on corrosion behavior of Ti-6Al-4 V samples fabricated by the laser-powder bed fusion (L-PBF) process and also after heat treatment at 800 °C for 1.5 h and subsequent cooling in furnace. While there was martensitic ( α ′) phase in the as-built condition, there was dual phase microstructure of α + β phase after heat treatment. Corrosion testing was carried out in Ringer’s solution. Electrochemical impedance spectroscopy (EIS) revealed that after heat treatment, the charge-transfer resistance increased from 98096 to 310130 Ω.cm 2 , due to increase in the oxide layer thickness. The Tafel plot showed a noticeable reduction in corrosion of the heat-treated samples. It was observed by x-ray photoelectron spectroscopy that there was an increase in atomic percentage of Ti, Al, and Oxygen, and decrease in their full width at half maximum, following heat treatment. The ductility of the heat-treated samples under compression was more than double than that of the as-built sample. While the yield strength in compression of heat-treated samples was lower, the compressive strength was higher than that of the as-built sample. Thus, L-PBF process combined with heat treatment can be utilized to fabricate high corrosion resistant Ti-6Al-4 V bioimplants.