Geometrical compatibility factor analysis of paired extension twins in extruded Mg-3Al-1Zn alloys

Recently, geometrical compatibility factor (m') has been used to characterize local strain compatibility between paired twins formed in rolled Mg alloys with basal texture. High m' and m' rank were present in most cases, suggesting that m' plays an important role in twin pair formation. The present study aims to extend the understanding of the effects of m' and grain boundary (GB) misorientation angle on twin pair formation in an extruded Mg alloy with basal fiber texture. 106 sets of paired twins were extracted from electron backscatter diffraction (EBSD) data and were analyzed. The results show that m' of paired twins distributes in a wide range (-0.5 to 1) in extruded Mg alloys due to the presence of a large fraction of high angle GBs. About 60% of twin pairs have the first m' rank, implying that m' is still an important factor for variant selection of paired twins in extruded Mg alloys. The distribution of m' with SF rank was also analyzed, showing that more than half of twin pairs are located in the left-top corner with m' > 0.6 and SF either rank one or two, which confirms that simultaneously high SF and high is favorable for twin pair formation in extruded Mg alloys. (C) 2015 Elsevier Ltd. All rights reserved.