Microstructure and Strengthening Mechanisms of Nanolamellar Structures in Ultrastrong Drawn Iron Wires

Abstract Ultrastrong pure iron wires have been produced with a strength of 1.8 GPa with a strain of 10.35. Based on microstructural observation and quantified structural parameters, the strengthening mechanisms and strength-structure relationship have been analyzed. It is found that the fiber texture intensity, boundary spacing and boundary misorientation tend to saturation due to the boundary junction motion when the drawing strain exceeds 8.89. The dislocation density in the ferrite cells/lamellae increases to ~ 3.6 × 1015 m−2 at a drawing strain of 10.35 without saturation. Based on the systematic microstructural characterization and quantification, the d−1 or (2d)−0.5 boundary strengthening plus forest hardening are discussed.