Statistical analysis of anomalous tension twin and twin transmission in pure Mg sheet for various grain sizes and strain rates
(1. Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China;
2. Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China)
2. Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China)
Abstract: A statistical analysis of the twinning behavior in a basal-textured Mg sheet under hard orientation loading was performed at strain rates of 1×10-5 and 1×10-1 s-1 with grain sizes of 70 and 20 μm. There were 1609 tension twins identified including adequate (51%) anomalous twins (Schmid factor m<0). Twin variant selection exhibited almost no grain size or strain rate effects. Most twin variants (74%) correlated well with the proposed normalized Schmid factor (mnor). The Luster-Morris parameter (m′) values failed to correlate with the twin transmission, while 96% of transmitted pairs exhibited large mnor or normalized m′ (m′nor) values. Twin transmission occurred more frequently at lower grain boundary misorientation angles (10°-30°). The active anomalous twins correlated well with m of the prismatic slip. The present work provided a statistical perspective that, the mnor and m′nor can correlate the anomalous twinning rather than m and m′. The local condition also played a critical role in anomalous twinning behavior.
Key words: Mg; anomalous twin; twin transmission; Schmid factor; Luster-Morris parameter