伸線加工におけるマグネシウム多結晶の塑性変形と欠陥生成のMD解析

抄録

Wiredrawing is a conventional plastic working method to produce metal wires, but a further improvement in strength and functionality of wires can be achieved by producing finer wires with nano-meter diameter. In particular, ultra-fine wire made of magnesium (Mg) and its alloy is expected for industrial purpose, including medical equipment. However, grain boundaries and crystal defects such as dislocations and twins in Mg and Mg alloys will significantly influence overall performance of such ultrafine wires. We are clarifying the deformation mechanism, considering the effect of grain size. Conventional wire drawing conditions were applied to a nano-sized pure Mg model. Molecular dynamics (MD) simulations with EAM potentials and simulations were performed by changing the grain size. In the results, the grain rotation due to twinning occurs so that the <1010> direction is coincided with the drawing direction. This result agrees well with the experimental texture obtained in the wiredrawing of Mg. In conclusion, wiredrawing process in nano-polycrystal includes little basal slip deformation, but instead twinning and grain boundary sliding mainly occur. We observed that a certain texture is also developing in the nano-polycrystals.