チタンおよびマグネシウムにおける(c+a)転位芯構造の分子動力学シミュレーション

To clarify the activity of the secondary pyramidal slip system in magnesium and titanium, core structures of (c+a) edge and (c+a) screw dislocations have been investigated by molecular dynamics method. The Lennard-Jones type and Finnis-Sinclair type potentials were employed. Stabled core structures were obtained in various temperature ranges. The (c+a) edge dislocation in magnesium has two kinds of core structures at 0 K; one is perfect dislocation (Type–A) and the other two 1/2 (c+a) partial dislocations (Type–B) . The type–A core structure expands to the basal plane with increasing temperature, while the type–B core is stable at higher temperatures. In the case of titanium, (c+a) edge-dislocation shows perfect dislocation independent of initial core structure and temperature. Furthermore, it never moves by applying strain. This behavior is different from the previous result of magnesium that the Type–A core changes to two partial dislocations (Type–B) and moves on the (1122) slip plane by applying strain, and the Type–B core slips without a change of structures. In the case of the (c+a) screw-dislocation, the core structures of titanium and magnesium expand on two first order pyramidal planes at 0 K, and they change to the structure expanded on a secondary pyramidal plane with increasing temperature. The activities of the secondary pyramidal slip system in titanium and magnesium can be explained from the difference of (c+a) edge dislocation core structures.