Fig. 1 XRD analysis of the alloy exposed to Se vapor at 700 °C for 100 h

Fig. 2 Surfaces of alloy exposed in Se steam at 700 °C with a 0.4 mg/cm2 Se for 100 h, b 1 mg/cm2 Se for 100 h, and c 2 mg/cm2 Se for 100 h, d 4 mg/cm2 Se for 100 h, e 2 mg/cm2 Se for 500 h, f 2 mg/cm2 Se for 1000 h

Fig. 3 Cross-sectional morphologies of the reaction layers and corresponding elemental analysis for the alloy exposed at 700 °C for 100 h with 2 mg/cm2 Se

Fig. 4 Cross-sectional morphologies of the reaction layers and corresponding elemental analysis for the alloy exposed at 700 °C for 500 h with 2 mg/cm2 Se

Fig. 5 Cross-sectional morphologies of the reaction layers and corresponding elemental analysis for the alloy exposed at 700 °C for 1000 h with 2 mg/cm2 Se

Fig. 6 Cross-sectional morphologies of the inner reaction layer exposed at 700 °C for 500 h with 2 mg/cm2 Se

Fig. 7 TEM analysis of products in the inner reaction layer of the alloy subjected to 2 mg/cm2 Se annealed at 700 °C for 500 h: a morphology of the inner reaction layer, the EDS analysis for the point A b and B c in Fig. 6a, d and e SAED pattern analysis for point A in Fig. 6a, and point B in Fig. 6a f and g

Fig. 8 Yield strength and ultimate tensile strength of the alloy exposed at 700 °C: a for 100 h with various Se contents, b with various aging time (Se: 2 mg/cm2)

Fig. 9 Cross-sectional fracture morphologies of the alloy exposed in 2 mg/cm2 Se vapor at 700 °C for a 100 h, b 500 h, c 1000 h

Fig. 10 Calculated binding energy and segregation energy for atomic Te and Se at various sites of GBs: a Σ3 (1 1 1), b Σ5 (0 2 1), c Σ11 (1 1 $\overline{3 }$) GBs. (*The positions of various atomic sites and the date for Te calculation can be referred to the previous Ref. [21])