Effect of strain rate and temperature on the flow stress of beta-phase titanium-hydrogen alloys

Compression tests were carried out on seven titanium-hydrogen alloys containing hydrogen concentrations up to 31 at. pct. All the experiments were performed within the beta-phase field at strain rates of 0.001 to 1.0 s(-1). The dependences of the steady-state flow stress on strain rate, temperature, and hydrogen concentration were determined. The strain rate sensitivity increases with temperature but decreases with hydrogen concentration. The experimental activation energy of deformation decreases when the flow stress or strain rate is increased. At a fixed strain rate, it decreases when the hydrogen concentration is increased. However, when measured at a fixed steady-state stress, the activation energies are nearly the same for all the alloys. The steady-state flow stress increases with hydrogen concentration as can be expressed by both linear and quadratic dependences. The flow behavior of the alloys can also be described in terms of thermally activated glide and the relation epsilon over dot = K sigma(4) exp (-Delta H-0/kT) exp (nu sigma/kT) where the constants nu and Delta H-0 are independent of hydrogen concentration, while the parameter K decreases exponentially when the hydrogen concentration is increased.