Unconfined Twist: a Simple Method to Prepare Ultrafine Grained Metallic Materials

摘要

A new simple method - unconfined twist was employed to prepare ultrafine grained (UFG) Fe wire. A coarse grained (CG) Fe wire with a diameter of 0.85 mm was fixed at one end, and twisted at the other end. After maximum twist before fracture, in the cross-sectional plane, concentrically deformed layers with a width of several micrometers formed surrounding the center axis of the wire. The near-surface deformed layers consist of lamella grains with a width in submicrometer range. In the longitudinal plane, deformed bands (with a width of several micrometers) formed uniformly, which were composed of lamella crystallites (with a width in submicrometer range). The tensile yield strength and ultimate strength of the twisted Fe wire are increased by about 150 % and 100 % compared with the values of its CG counterpart.