Magnetic and transformation behaviour of duplex stainless steels under non-isothermal conditions and temperature-fluctuation monitoring

Samples have been thermally aged between 500 °C and 600 °C and between 650 °C and 800 °C, respectively. The morphologies of the (γ2 + σ) eutectoid aggregates are temperature-dependent and the sigma phase undergoes continuous changes in both dimension and composition. As ageing proceeds, the sigma phase is gradually enriched in Fe, Mo and Ni and depleted in Cr. The patterns of change in the contents of these elements are affected by other alloying elements. Mo, like Ni and Cr, may enhance deformation twinning in bcc ferrite. Once the spinodal microstructure reaches steady-state growth, its influence on structure-sensitive magnetic properties dies away.