Effect of pre-strain on the ageing behavior of directly quenched copper containing micro-alloyed steel

Present investigation concerns the effect of pre-strain on the precipitation of copper during ageing of directly quenched Ti–B micro-alloyed steels. The differential scanning calorimetric study of the directly quenched samples reveals that copper precipitation occurs between 350–500 °C. Pre-straining of the directly quenched samples broadens the temperature range within which the peaks for copper precipitation overlap with the peaks due to other low temperature reactions like recovery and/or tempering. 50% pre-straining of 1.5 wt.% copper added steel prior to ageing triggered the precipitation reaction at a temperature ∼ 350 °C with pronounced decrease in the activation energy values from 182 to 126 kJ/mol. Micro-structural investigations have revealed the formation of cell structures within the martensite laths after ageing of the pre-strained directly quenched samples. While pre-straining has increased the strength with concomitant deterioration in ductility; ageing of the pre-strained samples has revealed perceptible improvement in elongation.