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

Abstract

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) α-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 α-Ti crystals as substitutional and interstitial elements, respectively. These solution elements caused a remarkable increment of the lattice constant of α-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.

 

This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 65 (2018) 746–755.