• Lentz, M.; Coelho, R.S.; Camin, B.; Fahrensohn, C.; Schaefer, N.; Selve, S.; Link, T.; Beyerlein, I.J.; Reimers, W.: In-situ,ex-situ EBSD and (HR-)TEM analyses of primary, secondary and tertiary twin development in an Mg–4 wt % Li alloy. Materials Science and Engineering A 610 (2014), p. 54-64


This study presents experimental evidence for the sequence of activation and the evolution of primary tension (TTW), secondary compression (CTW) and tertiary double twinning (DTW) in an extruded Mg–4 wt%Li alloy during uniaxial compression by means of in-situ and ex-situ EBSD and (HR-)TEM. In-situ EBSD analysis reveals that the secondary CTWs propagate very slowly ,while the tertiary DTWs propagate faster once nucleated. Thereby, when DTW-ing overtakes the CTW, CTW boundary migration stops, indicating that the thickness of the CTW is limited by the onset of internal DTW-ing.This finding confirms some prior proposals based on post-mortem analyses. High-resolution (HR-)TEM analysis of a 18% compressed sample reveals significant basal slip activity and a high amount of basal stacking faults within the primary TTW as well as within the secondary CTW. Additionally, the HR-TEM analysis showed a large amount of basa ldislocations within the area of the CTW-DTW transition.These findings give strong experimental evidence that the observed predominance of type 1 DTW-ing is related to the dissociation of extended basal dislocations.