Corrosion Behavior of Titanium Alloys Containing Boron Additions in Simulated Physiological Environments
Authors:Karyna Banuelos, Matthew Borgialli, Sevanne Calle, Hannah Leu, Obed Villalpando, Travis Voorhees, Morgan Wong
Mentor:Vilupanur A. Ravi, Department Chair of Chemical & Materials Engineering, California State Polytechnic University Pomona
Titanium and its alloys are known for their specific strength and excellent corrosion resistance. Due to these properties, titanium has become one of the leading materials for biomedical implants, specifically Ti-6Al-4V. The Ti-6Al-4V (Ti-64) alloy is an α+β alloy and is thus expected to exhibit traits from both the -phase (hexagonal close packed) and -phase (body centered cubic) alloy (Ti-5Al-5V-5Mo-3Cr). Commercially pure titanium (CP Ti), is an α alloy (hexagonal close packed crystal structure) that has excellent corrosion resistance, but is not very strong. Ti-5Al-5V-5Mo-3Cr (Ti-5553) is a β alloy (body centered cubic) that has promising mechanical properties. Recently, a new class of titanium alloys containing boron as an alloying element has been investigated for improvements in strength and stiffness. It has been shown that the addition of boron in the 0-1.2 wt.% range dramatically decreases the alloy grain size while increasing the Young’s modulus, yield strength, and ultimate tensile strength of the α, α+β, and β alloys when compared to the base alloys. Research at Cal Poly Pomona has been focused on evaluating the corrosion behavior of these unique alloys. Our data shows that none of the alloys pit under the modified ASTM F2129-08 protocol in different saline solutions. To characterize the pitting potentials of our alloys, a more aggressive test is conducted at a higher voltage. For α+β and β titanium alloys, the addition of boron decreased the pitting potential; however, the alpha alloys (0 and 0.1 B) did not pit under the same conditions. This presentation will present the results of electrochemical corrosion tests of these titanium alloys in saline solutions and discuss them with relevance to heir chemical composition.