C. Tian; H. Wang; P.-L. Sun; M. Freund; M. Hans; M. Sarebanzadeh; Z. Xie; G. Mohanty; J. Schwiedrzik; S. Korte-Kerzel
Acta Materialia 316 (2026) 122498
Grain boundaries play an important role in determining mechanical properties of materials. To investigate the behavior of a single grain boundary, micropillar compression on bi-crystals has been widely applied, which however, mainly focuses on face-centered cubic metals. In this work, we investigate the influence of micropillar size, strain rate and temperature on deformation behavior of an Fe-2.4 wt.% Si bi-crystal with a high angle grain boundary and its paired single crystals. Tests were carried out at room temperature and -80 °C, nominal micropillar sizes were 1 µm, 2 µm and 4 µm, while strain rates were 0.001 s−1, 0.01 s−1 and 0.1 s−1. Slip trace analysis reveals slip transmission across the grain boundary in bi-crystalline pillars. The transmitted slip systems can be different from those activated in single crystals depending on orientation. The identified transmission pair has a high transmission factor and is insensitive to strain rate and temperature, but dependent on pillar size. In contrast, the difference in yield strength between bi-crystals and single crystals is more closely related to testing parameters. For single crystals, smaller pillars can activate slip systems with a lower Schmid factor and slip traces become wavy due to cross-slip at a sub-ambient temperature.