Abstract
As-HIP’ed cast α+β type Ti-6Al-7Nb and Ti-6Al-4V for dental applications were conducted with general thermochemical heat processing (THP) and THP combined with a post heat processing (THPH) to refine their microstructure and improved their fatigue strength without decreasing ductility. Then, the fatigue crack initiation and small fatigue crack propagation behaviors of HIP’ed cast Ti-6Al-7Nb and Ti-6Al-4V were mainly investigated in this study.
Fatigue limits of HIP’ed cast Ti-6Al-7Nb and cast Ti-6Al-4V are improved about 40% by THP and THPH as compared with those of as-HIP’ed ones. Fatigue crack initiation and small fatigue crack propagation resistance of HIP’ed cast Ti-6Al-7Nb and Ti-6Al-4V is improved remarkably by THP and THPH as compared with those of as-HIP’ed ones because the effective slip length under the cyclic stress is decreased due to refined microstructure by THP and THPH, and the slips occur uniformly. Fatigue crack initiation and small fatigue crack propagation life of HIP’ed cast Ti-6Al-7Nb and Ti-6Al-4V conducted with THP and THPH are around 80∼90% of the total fatigue life. They increase twice as much as those of as-HIP’ed cast Ti-6Al-7Nb and Ti-6Al-4V (i.e. around 40%).
