Dynamic recrystallization (DRX), driven by the dynamic stored energy of cold work, promotes shear localization. However, the influence of twinning remains to be investigated. We consider two model materials under impact, pure Titanium and a Ti6Al4V alloy, for which the extent of twinning and DRX differs vastly. A grain-scale finite element model shows that twinning delays DRX and consequently strain localization. Moreover, the calculated temperature elevations (local and global) remain very modest until the onset of failure. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.