Low-frequency internal friction of α+β titanium alloy SP-700

Internal friction of a commercial alpha + beta two-phase titanium alloy SP-700 has been measured at frequencies around 1 Hz in the temperature range from 90 to 400 K to characterize the damping capacity of the material. Two components of internal friction have been observed for specimens quenched from temperatures around the alpha/beta transus (1173 K): a well-defined peak located at 129 K and a broader one around 200 K. The magnitude of the former peak is increased by hydrogen charging, and the activation energy is close to that of the diffusion of hydrogen in p-titanium. The peak is thus attributed to stress-induced redistribution of hydrogen atoms in beta phase. The component at 200 K appears when the alloy has been quenched from temperatures around the transus but does not when cooled slowly. This component is due either to defects in alpha" martensite produced by quenching or to interfaces between alpha" and the beta phases. The damping capacity can be as high as 10(-2) at low temperatures but is much lower at room temperature. (C) 1999 Elsevier Science S.A. All rights reserved.