Development of Titanium Alloys with Low Elastic Modulus and High Corrosion Resistance designed on the Basis of Quantum Chemistry Theory

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To develop new Ti alloys with low elastic modulus and high corrosion resistance, Ti-Zr binary alloys with Zr content of 0, 20, 40, 60, 70, 80, 100 at.% were prepared and their density, Young's modulus, Poisson's ratio and Vickers microhardness were investigated. Primary experimental results were as follows.1. DensityThe density vs. composition curve for the Ti-Zr binary alloys slightly deviated positively from the straight baseline connecting the two points on both ends for pure Ti and pure Zr. It is noted that the degree of deviation from the straight baseline was slightly greater in the Ti-rich region compared to the Zr-rich region.2. HardnessHardness of the as-cast pure Ti and Zr were 157 VHN and 196 VHN, respectively. The alloying addition of 20 at.% Zr to Ti drastically increased hardness, indicating that a great deal of solid solution hardening occurred. Further addition of Zr further increased Vickers hardness up to about 370 VHN at Ti-60 at.% Zr composition. Similar solid solution hardening was observed when Zr was alloyed with Ti. However, magnitude of increase in hardness was much weaker in the Zr-rich region compared to the Ti-rich region.3. Young's modulus and Poisson's ratioYoung's modulus of pure Ti was significantly higher than that of pure Zr. By alloying Ti with Zr, Young's modulus markedly decreased and the minimum Young's modulus of about 89 GPa was obtained at the Ti-60 at.% Zr composition. On the other hand, Poisson's ratio of pure Ti was significantly lower than that of pure Zr. By alloying Ti with Zr, Poisson's ratio markedly increased and the maximum Poisson's ratio of about 0.343 was obtained at the Ti-60 at.% Zr composition.