Characterization of the transport processes in Fe-Cr-Ni stainless steel

Measurements of electrical resistivity, X-ray diffraction and DTA were used to characterize the transport processes developed in an Fe-12.1 Cr-7.37 Ni (wt. %) stainless steel during heating from 300 to 980 K and subsequently during cooling to room temperature. The results revealed that this steel exhibits two transport regions during heating and only one during cooling. In case of heating, the first transition region (observed in the temperature range 650-730 K) is not to a structural but may be a magnetic transition. The second transition region (observed in the temperature range 885-915 Kj is ascribed to the austenitic structural transformation. During cooling, a unique transition region was observed in the range 560-434 K. This was attributed to the martensitic transformation which may also be associated with a magnetic transition. From the DTA data, the effective activation energy for the austenitic transformation was determined to be 459.3 kJ mol(-1). In the temperature ranges other than the transition regions the electrical resistivity fits a linear equation rather than the Bloch-Gruneisen equation. (C) 1997 Elsevier Science S.A.