Abstract
The combined effect of O and N additions on the fatigue properties with Ti-15%Zr-4%Nb-4%Ta-0.2%Pd-0.2%O-0.05%N and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd-0.2%O alloys were investigated by fatigue testing in a physiological saline solution at 310 K. The fatigue test was carried out under the condition of a tension to tension mode with a sine wave at a stress ratio of 0.1 and at a frequency of 2 Hz and 10 Hz in Eagle’s medium solution using an environment cell with 90%N2+5%CO2+5%O2 gas bubbling. Further the effect of human hip joint load profile estimated by analysis of forces and actions for human hip joint on the corrosion fatigue strength were examined.
The effect of heat treatment on the mechanical strength of the new Ti alloys were investigated. As the solution treatment temperature increased the ductility of Ti-Zr and Ti-Sn alloys decreased. After solution treatment, the mechanical strength of Ti-Zr and Ti-Sn alloys did not change much as the aging time and the aging temperature increased. The additions of O and N to the new Ti alloys and heat treatment substantially increased the ultimate tensile strength to 1000 MPa. Also, the total elongation was more than 10%. The fatigue strength of Ti-Sn alloy added 0.2%O, 0.005%N and Ti-Zr alloy added 0.2%O, 0.05%N at 108 cycles was 1050 MPa and 950 MPa, respectively. The effect of frequency on the fatigue strength at 2 Hz and 10 Hz was almost similar. Moreover, the fatigue strengths ware almost the same for sine wave and human hip joint load profile in both Ti-Zr and Ti-Sn alloys.
