伸線加工メカニズムと格子欠陥挙動に関するMD解析

抄録

Wiredrawing is one of plastic working methods, and it has been used in a wide range of engineering fields. Nowadays, the wiredrawing technique is reducing wire diameter down to nanometer scale and will be providing with high mechanical function. So, understanding microscopic phenomenon of metallic materials and the mechanism inside the wire becomes more important. The main purpose of this research is to evaluate behavior of dislocation density when nano-sized wiredrawing of single crystal is performed with the change of crystal orientation and temperature. The authors use molecular dynamics (MD) which reproduces atomic structure and observe the dislocation behavior inside wire during drawing process. Wiredrawing condition is applied to iron single crystal (α-Fe) with many-body (FS) potential. In actual processing, the wire material is exposed to high temperatures due to severe friction and such temperature rise will have large influence on the dislocation behavior. From simulated results, we found that, as the temperature is increased, the dislocation density of drawing in <100> or <110> direction shows a linear increase with increase of system temperature. In drawing in <111> directions, one long dislocation line occurs from the surface. But each dislocation does not collide inside. Therefore, dislocation density does not increase because one long dislocation disappears on the wire surface. As a conclusion of this study, nanowire models clarify the temperature dependence of dislocation density in the wire.