2016 年 57 巻 12 号 p. 1986-1992
Young's modulus (E), shear modulus (G), bulk modulus (K) and Poisson's ratio (ν) of Ti-Zr binary alloys containing 20, 40, 50, 60, 70 and 80 at% Zr and component pure metals (Ti, Zr) prepared by arc-melting followed by solidification process were determined precisely by ultrasonic sound velocity measurements. X-ray diffraction analysis showed that all the as-solidified alloys and pure metals were with a single-phase structure of the hexagonal close-packed lattice (martensitically formed α′-phase). The alloying addition of Zr to Ti effectively decreased both E and G values with their minimum values of 89.5 ± 1.0 GPa and 33.3 ± 0.4 GPa, respectively, being recorded at the same composition Ti-60 at% Zr. On the other hand, K values decreased slightly when the concentration of Zr was increased from 20 to nearly 50 at% and further increases in Zr concentration did not change K values greatly. The observed variations of Young's modulus with Zr concentration in the entire range of composition were well interpreted in terms of density (ρ), Debye temperature (θD) and concentration of atoms (n) in each alloy. The quantity ρθD2n−2/3 was revealed to be a good measure in predicting the tendency of variations of Young's modulus with composition in this binary system.
