The Corrosion Behavior Of TiZrAlV Alloys

With the development of modern industry, the working environment of materials is becoming harsher. Ti alloys have received considerable attention because of their unique properties, such as excellent shape memory properties, good superconductivity, hydrogen storage and satisfactory biocompatibility. Due to their durable and reliable corrosion resistance in many corrective environments, Ti alloys have been widely used in aerospace, marine fileds and offshore units, biomedical, chemical process, energy system and many other fields. Although there are many types of Ti alloys, the research on the corrosion resistant Ti alloys is so insufficient that the types of corrosion resistant Ti alloy are quite small and the commercialization of corrosion resistant Ti alloy are negligible. In this dissertation, based on Ti-6Al-4V alloy, a series of TiZrAlV alloys were designed through replaced Ti element by different amount of Zr element. Meanwhile, the influences of Zr addition and heat treatment on the microstructure and corrosion behavior were investigated.The results show that the composition is a major factor affecting the corrosion performance of TiZrAlV alloys. The oxide formed can improve the corrosion resistance of the original oxide layer after Zr addition. The improvement of the corrosion resistance of TiZrAlV alloys can be attributed to the optimization of the oxide film. The passivation current density of the alloys decreased and the alloys were more prone to pitting with increased Zr content.Comparing the corrosion properties of the alloys after different heat treatment process(annealing, solution treatment and solution-aging treatment), the acicular α" phase generated after solution treatment has the best corrosion resistance. The corrosion potential of 20 Zr decreased and the corrosion current density increased with increased annealing temperature. Therefore, the corrosion properties of the 20 Zr alloys decreased with increased annealing temperature. The volume fraction of β phase as well as the grain size was identified as the main factor affecting the corrosion performance of the 20 Zr alloys. The corrosion resistance decreased with the increase in grain size and the volume fraction of β phase. Although the phase ratio and the microstructure of the 51 Zr alloy have been changed by different annealing temperature, no significant changes occurred in the breakdown potential, corrosion current density and weight loss of the 51 Zr alloy. Hence,the annealing heat treatment has little effect on the corrosion behavior of the 51 Zr alloy.