which leads to severe reduction in the
impact toughness of DSS base metal. The average toughness value absorbed in the tested sample was 52.33 Joules
which is far less than the toughness of the base metal which is free from sigma in the as received condition. The
absorbed energy and fractured surface of the sigma contained sample is shown in Fig. 16. (a) and (b). EDX
analysis was carried out in the sigma phase and the nearer locations. The measured locations in EDX analysis are
indicated in Fig. 17 (a) and (b). The sigma phase contains the excessive accumulation of chromium and
molybdenum atoms in it which causes depletion in the surrounding regions which is shown in Fig. 18. The
segregation of major alloying elements in the sigma phase and nearer ferrite austenite phases is shown in Table. 3.
Fig. 17. (a) Base metal of DSS with sigma precipitation; (b) SEM image
Table. 3. The EDAX analysis of sigma phase
Element
Percentage amount in different phases
Region 1 Region 2 Region 1 Region 2 Region 1 Region 2
Cr 25.61