The Effect of Hydrogen on Dynamic Recrystallization in α-Titanium Alloys
The influence of hydrogen content on the mechanical properties and size of dynamically recrystallized grains in commercially pure (CP) titanium and Ti-5Al-2.5Sn alloy was investigated. The alloys with hydrogen contents from 0.1 to 5.2 at.% were deformed in the a-field at temperatures of 650°, 750°С with initial strain rates of 5×10-4 s-1. A decrease of the deformation temperature leads to a reduction in grain size and to a stress increase for all compositions. This is in good agreement with the well known relation between the recrystallized grain size (d) and the steady flow stress ss=kd-n. At a given test temperature the steady state flow stress is four times lower and the grain size is about ten times greater in CP titanium in comparison with the Ti-5Al- 2.5Sn alloy. Hydrogen alloying of the Ti-5Al-2.5Sn alloy does not lead to a noticeable change in ss and d. However, an increase in hydrogen content from 0.1 to 5.2 at.% in CP titanium leads not only to a decrease in grain size by a factor of 2 but also to a decrease in flow stress (about 28%). This result is not in agreement with the above relation. This unusual behaviour may be due to two reasons: the influence of hydrogen on grain growth and the hydrogen effect on dynamic strain ageing. Both these effects are stronger in CP titanium.
B. Bacroix, J.H. Driver, R. Le Gall, Cl. Maurice, R. Penelle, H. Réglé and L. Tabourot
M. A. Murzinova et al., "The Effect of Hydrogen on Dynamic Recrystallization in α-Titanium Alloys ", Materials Science Forum, Vols. 467-470, pp. 1223-1228, 2004