Comparison of precipitation kinetics and strengthening in an Fe-0.8%Cu alloy and a 0.8 % Cu-containing low-carbon steel

The precipitation kinetics and associated change in mechanical properties (hardening and strain hardening rate) have-been compared in a Fe-Cu alloy and a Cu-containing low-carbon steel of identical copper content (0.8wt%). A combination of experimental techniques (TEM, Small Angle X-ray Scattering, tensile tests) have been used to quantitatively determine the precipitation phenomena during ageing at 500degreesC, including the influence of the presence of dislocations prior to the ageing treatment. The precipitation phenomena are shown to be qualitatively identical, in terms of nucleation size, influence of dislocations on the precipitation reaction, or influence of precipitation on the strain hardening rate. However, the growth kinetics of precipitates is shown to be much faster in the steel. Similarly, the time to peak hardness is reduced in the steel. Further, the net precipitation hardening capability is reduced in the steel as compared to the Fe-Cu alloy. The results are discussed in terms of the influence of Mn and C on the precipitation and hardening processes.