This work reports the refinement of pearlite structure into nanostructure using electropulsing. Nanostructured pearlitic steel wires possess nanoscale lamellae or nanoscale grain microstructures. Fabrication of nanostructures by severe plastic deformation and lamellar to grain transformation have been investigated. It is suggested that an aligned pearlite structure is preferred in severe plastic deformation. The lamellar to grain transformation is controlled by diffusion of carbon within cementite and also from cementite to ferrite phases.Carbon mobility is changed by mechanical, thermal and electrical states. The interface between nanoscale sub-grains in the ferrite phase has considerable carbon content. Numerical calculations and experimental observations demonstrated these mechanisms.

The present paper investigates the use of electric current treatment in improving the drawability of plain carbon steel wire for high strength steel applications. The mechanical properties for wires of composition 0.80C 0.65Mn 0.27Si wt.% of diameters 4.09 and 3.00 mm dry drawn from 10.00 mm rods are characterised. The total number of passes for 4.09 and 3.00 mm diameter wires are 7 and 10 respectively resulting in true strains of 1.79 and 2.41. Samples are treated with electric currents in-between the two drawing stages of 4.09 and 3.00 mm, and tested at both stages in tension, torsion and reverse bending along with control samples for comparison. The applied currents are pulsed at a frequency of 100 Hz with each pulse being approximated by a square wave of loading width 80µs and modest current densities of 7.96 Amm −2 . Thus the influence of electric current on the drawability of plain carbon steel wire is assessed between stages of reduction.

The angle misorientation distribution of martensite formed from electric current treated and nontreated austenite samples are studied using electron backscatter diffraction. The electric currents are pulsed with loading width of 80 µs, at a frequency of 100 Hz and current density of 4.21 A/mm 2 supplied by a DC Voltage. The majority of angle misorientations are < 5 o and exist within the martensite grains, while only minority of all misorientations are derived from the prior austenite grain boundary and were found to lie in the range 20-50 o. Distinct textures develop in both electric current treated and non-treated samples with increased quenching temperature. Analysis of the prior austenite show reduced grain sizes in the electric current treated samples at all quenching temperatures considered.

Dry drawing is an essential procedure in transforming steel rods into wires. However, it results in extensive work hardening and wires requiring patenting to restore the microstructure and hence ductility to prevent premature failure. This increases processing time and high stresses limit service life of drawing dies. However, the application of pulsed electric current has been reported to reduce the stress required to deform a metal in uniaxial tension and enhance deformation making the material easier to work. This could slow the work hardening rate of wires and therefore reduce the necessity for patenting and reduce wear on dies. To date, confined usage of the technique suggests it is either not well understood or lacks its acclaimed benefits. This review was submitted as part of the 2018 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.

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