Hydrogen Influence on Martensitic Transformation and Shape Memory Effect in Titanium Alloys

Moscow State University of Aviation Technology after K. Tsiolkovsky, Metals Science Department, Petrovka Str. 27, K-31, Moscow 103767, Russia

Abstract

The influence of hydrogen alloying on the habitudes of martensitic transformation (MT) in (α+β)- titanium alloys was investigated, ft was shown, that increased hydrogen content in titanium alloys lowered the temperature and widened the range of direct and reverse MT, it also lowers the critical cooling rate over which the MT occurred. Thus, hydrogen in the process of cooling facilitates the (β→α")-transformation, and it can be realized even in alloys, in which without hydrogen the (β→α')-martensitic transformation takes place. The dislocation mechanism of deformation with invariant lattice during MT mostly changes to the twinning. The increased hydrogen content lowers the absolute value of the main deformations of (β→α") MT and one of them tends to zero, the habit of a crystal has more perfect structure and higher mobility. Hydrogen enriched alloys have necessary conditions for conservation of coherence on interface boundaries in the range of (β→α") MT. In its term, it causes near complete shape memory effect realization. So, the hydrogen increased titanium alloys of martensit class have recovering deformation effect in 1.5 times higher than alloys with ordinary hydrogen content.