Influence of heat treatment on Cr and Fe-rich precipitates in thermally aged duplex steels

In this investigation, three different heat treatment conditions were evaluated to correlate the microstructural changes of duplex steels with their mechanical properties. In the first heat treatment condition, the samples were aged at 475°C up to 1000 h. This resulted in the formation of alpha and alpha-prime precipitates in ferrite matrix due to spinodal decomposition, which in turn embrittled the samples. In the second heat treatment condition, the embrittled samples were reversion heat-treated at 550°C up to 120 min, which resulted in dissolution of the alpha and alpha-prime precipitates. This resulted in an increased ductility of samples. In the third heat treatment condition, the reversion heat-treated samples were re-aged at 475°C for 100 h in order to check applicability of reversion heat treatment. The results showed that spinodal decomposition again remained as the primary mechanism of embrittlement, and it was also found that there was not much difference in the re-embrittlement rate.