Strengthening Mechanisms of Powder Metallurgy Extruded CP Titanium Materials with Zirconium and Oxygen Solid Solution via Decomposition of ZrO2 Additives in Sintering

摘要

One of the representative high-strength titanium (Ti) alloys used as biomaterials is a commercial Ti-6Al-4V (Ti-64). It has, however, serious problems because Ti-64 contains vanadium, one of highly toxic elements, as the necessary additive to improve the mechanical strength. In this study, in order to develop a high-strength and biocompatible Ti alloy for application to biomaterials, powder metallurgy (PM) alpha-Ti material with zirconium (Zr) and oxygen (O) solid solution (Ti(Zr,O) alloy) was fabricated from the elemental mixture of CP Ti and ZrO2 powders. During solid-state sintering process, the additive ZrO2 particles were decomposed by reaction with CP Ti powder, and then Zr and O atoms were dissolved in the alpha-Ti crystals as substitutional and interstitial elements, respectively. These solution elements caused a remarkable increment of the lattice constant of alpha-Ti (hcp) crystal, and resulted in the significant improvement of tensile strength of Ti alloys. For example, Ti(Zr,O) alloy showed 0.2% yield stress of 1153 MPa when using CP Ti powder mixed with 3 wt.% ZrO2 particles, which was greatly high compared to PM CP Ti material with 0.2% YS of 463 MPa. In addition, the solid solution strengthening mechanism of this alloy was investigated in detail.