Abstract
Wiredrawing is successfully to producing high-strength and small-diameter wires. Products produced using this process are used in a wide range of industries. In recent years, miniaturization and weight reduction of components have progressed, and extra fine wires having a reduced diameter as well as high performance are required. Drawing limit of the current metallic wire is several micrometers in diameter, so realization of nanowire is nearly coming. When a metallic material undergoes plastic deformation, a phenomenon called dislocation occurs. Understanding the mechanism of dislocation is important for predicting mechanical properties of metallic materials. In this study, molecular dynamics method which can observe dynamic dislocation behavior is used. We are clarifying strengthening mechanism by dislocation concerning the effect of crystal orientation and temperature. Conventional wiredrawing condition is applied to nano-sized iron single crystal (α-Fe) model with many-body (FS) potential, and by changing the temperature conditions, some simulations are performed. In results, with temperature control, when the temperature is high, the number of dislocation lines inside the wire increases because SS (Statistically Stored) dislocations (including immobile dislocation, entanglement between dislocation lines, and etc.) increase by virtue of thermal activation in addition to GN (Geometrically Necessary) dislocations. With no temperature control, rapid temperature rise between the die and the wire is observed. This results agree well with the simulated case of actual (larger scale) processing. In conclusion, temperature dependence of the number of dislocations is clearly observed in the case of nanowires, where the influence of SS dislocation is dominant.
