High-cycle fatigue properties of beta Ti alloy 55Ti-30Nb-10Ta-5Zr, gum metal

This paper describes the fatigue properties of the beta titanium alloy 55Ti-30Nb-10Ta-5Zr, generally referred to as 'Gum Metal'. Rotating bending fatigue tests have been performed in laboratory air and in a 3% NaCl aqueous solution. The results obtained were compared with those of a conventional beta titanium alloy, Ti-22V-4Al. In tensile tests, 55Ti-30Nb-10Ta-5Zr indicated elasticity and microplasticity in the elastic region. Thus, the elastic modulus slightly decreased with an increasing strain, and the work hardening was minimal during plastic deformation. The mechanical properties of both of the alloys were comparable. The fatigue strength of 55Ti-30Nb-10Ta-5Zr in laboratory air was higher than that of Ti-22V-4Al, which could be attributed to the higher fatigue crack initiation resistance of 55Ti-30Nb-10Ta-5Zr than Ti-22V-4Al, while the resistance to small fatigue crack growth was similar. The fatigue strength of 55Ti-30Nb-10Ta-5Zr in laboratory air and in the 3% NaCl aqueous solution was analogous. In addition, corrosion pits were not observed in the run-out specimen in the 3% NaCl aqueous solution, indicating a high resistance of 55Ti-30Nb-10Ta-5Zr against corrosion fatigue.