Fig. 1. DL-EPR curves of as-received and solution treated specimens.

Fig. 2. Specimens' surface micrographs after IGC tests: (a) as-received specimen after DL-EPR test, (b) as-received specimen after oxalic acid etch test, (c) solution-treated specimen after DL-EPR test, and (d) solution-treated specimen after oxalic acid etch test.

Fig. 3. DL-EPR curves of the specimens aged at various temperatures for various times: (a) 550 °C, (b) 600 °C, (c) 650 °C, (d) 700 °C, and (e) 750 °C.

Fig. 4. Variation of Ra values calculated from DL-EPR curves with aging time at various aging temperatures.

Fig. 5. Comparison of Ra values and surface micrographs of the specimens aged at 650 °C for various times after DL-EPR and oxalic acid etch tests.

Fig. 6. Comparison of Ra values and surface micrographs of the specimens aged at different temperatures for 30 min after DL-EPR and oxalic acid etch tests.

Fig. 7. TTS curve of the stabilized ultra-pure 430LX FSS.

Fig. 8. SEM micrographs and EDS analysis results of the specimens aged at 650 °C for 30 min and 8 h after oxalic acid etch test: (a) SEM micrograph of the specimen aged for 30 min, (b) EDS analysis result of 'A' marked in (a), (c) SEM micrograph of the specimen aged for 8 h, and (d) EDS analysis result of 'B' marked in (c).

Fig. 9. TEM micrographs, EDS analysis results and SAED patterns of the precipitates along the grain boundaries in the specimens aged at 650 °C for 30 min and 8 h: (a) TEM micrograph of the intergranular precipitates in the specimen aged for 30 min, (b) EDS analysis result of 'A' marked in (a), (c) SAED pattern of 'A' marked in (a), (d) TEM micrograph of the intergranular precipitates in the specimen aged for 8 h, (e) EDS analysis result of 'B' marked in (d), and (f) SAED pattern of 'B' marked in (d).

Fig. 10. Schematic diagram illustrating the IGC mechanism of the stabilized ultra-pure 430LX FSS.