Effect of pre-strain on extension twinning behavior in an extruded AZ31 Mg alloy observed by in-situ EBSD.

The effect of pre-strain on extension twinning behavior in an extruded AZ31 Mg alloy was investigated in this study. Pre-compression along the radial direction (RD) and subsequently compression along the extrusion direction (ED) were carried out with quasi-static strain at room temperature. The twinning evolution was observed by in-situ electron backscatter diffraction (EBSD). The results showed that profuse basal <a> and pyramidal <c+a> dislocations were introduced after a 5% strain pre-compression along the RD. The pre-strain along the RD significantly hindered the nucleation of 10 1 ¯ 2 extension twins during subsequent compression along the ED, but had little effect on the growth of 10 1 ¯ 2 extension twins. The nucleation of 10 1 ¯ 2 extension twinning at a twin boundary facilitated by twin-twin interaction was confirmed. The increase of dislocation density of twinned area was more depended on basal <a> slip inside twins rather than twin-dislocation interaction, and the twin-twin interaction was an important source of dislocation multiplication. • The profuse dislocations are introduced into an extruded AZ31 bar by pre-compression along the radial direction. • The main dislocation types caused by pre-compression are basal <a> and pyramidal <c+a> dislocations. • The pre-introduced dislocations can hinder the nucleation of 10 1 ¯ 2 extension twins other than their growth. [ABSTRACT FROM AUTHOR]