Abstract
The present investigation concerns effect of prestrain on the precipitation of Cu during aging of directly air cooled Ti–B microalloyed steels. The differential scanning calorimetry studies allow to identify that precipitation of Cu is most prominent between 350 and 500°C. Prestraining of the directly air cooled samples has broadened the temperature range for Cu precipitation with perceptible overlapping with the peaks due to other low temperature reactions like recovery and/or tempering. Fifty per cent prestraining of 1·5 wt-%Cu added steel before aging triggered the precipitation reaction at a temperature ∼320°C with pronounced decrease in the activation energy values from 172 to 116 kJ mol−1. Microstructural changes due to prestraining are evident in the micrographs obtained from transmission electron microscope as deformed ferrite laths and formation of cell structures therein. While 15–50% prestraining has increased the strength without much deterioration in ductility; aging of the prestrained samples has improved the strength and ductility concomitantly.
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