High-Temperature-Creep Mechanism of TiNi

Polycrystalline specimens of the intermetallic compound TiNi were tested in tension in the temperature range 700°–1000°C. The specimens were observed to deform uniformly over the gage length until the very end of deformation, when it failed by necking. It was noted that the steady‐state flow stress was independent of the strain and was a function only of the temperature and strain rate. The shear strain rate $\mathrm{\gamma ̇}$ was given by ${\mathrm{\gamma ̇\propto \tau }}^n$ where n=3.0±0.2, r was the shear stress, and n was independent of temperature. The apparent activation energy for creep was found to be 60.0±3.0 kcal/mole and was independent of stress. The result strongly suggests that a viscous creep process, as first formulated by Weertman, is probably the rate‐controlling mechanism for this compound in the stress and temperature range investigated.