Atomic scale insights into the fracture behavior along 〈12-10〉 and 〈101-0〉 oriented twin boundaries in titanium

Abstract 〈 1 2 - 1 0 〉 and 〈 1 0 1 - 0 〉 oriented twin boundaries (TBs) have important roles in the modification of strength and ductility of HCP metallic materials. As microcracks may be prone to initiated from TBs, their intrinsic brittleness and ductility need to be studied. Combing atomistic simulations and theoretical calculations, it is demonstrated that the incipient crack propagation behavior along most of the two sets of TBs in HCP titanium is dominated by brittle mode at very low temperature. Nevertheless, significant dislocation activities in the later stage can hinder the crack propagation along 〈 1 2 - 1 0 〉 oriented TBs. Consequently, the ductility of 〈 1 2 - 1 0 〉 oriented TBs is generally superior to that of 〈 1 0 1 - 0 〉 oriented TBs. Furthermore, brittle-ductile transition occurs with the increase of strain rate and temperature due to dislocations emitted from the crack tip and TB site.