Effect of Tantalum Content on Mechanical and Corrosion Behavior of TI-6Al-3Nb-2Zr-1Mo-xTa Alloys

The microstructure, tensile properties, Charpy impact toughness and corrosion resistance of Ti-6Al-3Nb-2Zr-lMo-xTa (x=0, 0.2, 0.5, 1.0, 3.0, 5.0) alloys were investigated. The results indicate that except Ti-6Al-3Nb-2Zr-lMo-5Ta alloy with lamellar structure, the bimodal structure is observed in Ti-6Al-3Nb-2Zr-lMo-xTa (x=0, 0.2, 0.5, 1.0, 3.0) after hot deformation at a+fi region. The results of XRD patterns and selected area electron diffraction indicate that no new phase is identified after adding Ta, although the peaks of both a and,8 phases shift toward the low angle side with the increase of Ta content. For the Ti-6Al-3Nb-Zr-lMo-xTa alloy with bimodal structure, the yield strength (YS), ultimate tensile strength (UTS) and microhardness increase due to the increase of molybdenum equivalent (Mo[]). The influence trend of the Ta content on impact absorb energy is opposite to that on YS, UTS and microhardness. YS, UTS and microhardness are in consistent with the area of shear lip region in the impact fracture surface. When the Ta content is more than 1.0wt%, the corrosion resistance of Ti-6Al-3Nb-2Zr-lMo-xTa alloys decreases due to the increase of standard balancing potential difference between a and fi phases. After potentiodynamic polarization tests, the sample surface area is covered with lots of corrosion pits, which are mainly distributed in the a, grain interior and affl interface. Combining YS, impact toughness and corrosion performance, Ti-6Al-3Nb-2Zr-lMo-1 Ta alloy exhibits the optimized compatibility, suggesting its promising potential for marine applications.