The evolution of grain structures, especially the types of grain boundaries (GBs), during directional solidification is crucial to the electrical properties of multicrystalline silicon used for solar cells. To study this, the electric molten zone crystallization (EMZC) of silicon wafers at different drift speeds from 2 to 6 mm/min was considered. It was found that < 111 > orientation was dominant at the lower drift velocity, while < 112 > orientation at the higher drift velocity. Most of the non-Sigma GBs tended to align with the thermal gradient, but some tilted toward the unfavorable grains having higher interfacial energies. On the other hand, the tilted Sigma 3GBs tended to decrease during grain competition, except at the higher speed, where the twin nucleation became frequent. The competition of grains separated by Sigma GBs could be viewed as the interactions of GBs that two coherent Sigma 3(n) GBs turned into one Sigma 3(n)GB following certain relations as reported before. On the other hand, when Sigma GBs met non-Sigma GBs, the non-Sigma GBs remained which explained the decrease of Sigma GBs at the lower speed. (C) 2016 Elsevier B.V. All rights reserved.