Cold-drawn pearlitic steel wires are nanostructured and the flow stress at room temperature can reach values above 6 GPa. A typical characteristic of the nanostructured metals, is the low ductility and thermal stability. In order to optimize both the processing and application of the wires, the thermal behaviour is of interest. This has been studied by annealing the wires for 1h at temperatures from ambient temperature to 300 °C (573 K). It is expected that a raising temperature may lead to structural changes and a reduction in strength. The change in strength is however not expected to be large. For this reason we have applied a very precise technique to measure the tensile properties of the wires from a strain of 10~(-4) to the maximum strain of about 1-2%. The structural changes have also been followed to estimate and relate strength changes to changes in structural parameters and morphology.
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