# Effect of Heat Treatment on Microstructure and Creep Behavior of Fe-40 Ni-24 Cr Alloy
## 2 Experimental Procedure  
The materials used in this research were commercial Fe-40 Ni-24 Cr alloy (HAYNES(r) HR-120(r)) supplied by Haynes. The alloy received was in sheet form with dimensions 300 (l) \(\times\) 100 (w) \(\times\) 3 (t) mm using electrical discharge machining (EDM). Then the specimen underwent mounting, followed by grinding, polishing and etching in order to conduct microstructure investigation on the materials. Table S1 in the Supplementary Materials shows the chemical composition of the materials. The chemical composition was analyzed by using an optical emission spectrometer (OES). Then the specimens underwent solution treatment at temperatures 950 \({}^{\circ}\)C, 1000 \({}^{\circ}\)C, 1050 \({}^{\circ}\)C, 1100 \({}^{\circ}\)C, 1150 \({}^{\circ}\)C, 1200 \({}^{\circ}\)C, 1225 \({}^{\circ}\)C and 1250 \({}^{\circ}\)C with heating rate 1 \({}^{\circ}\)C/min for 3 h (significant to transform all the room temperature microstructures to austenitic structures), followed by a water quenching process. Hitachi SU8000 scanning electron microscope (SEM) and ZEISS-SUPRA 3 SVP field emission scanning electron microscope (FESEM) were used to analyze the microstructure detail and fracture morphology of the specimens. Energy-dispersive X-ray spectrometer (EDS) with FESEM was used to determine the chemical element in the specimens. The transmission electron microscope (TEM) that was used in the research was Tecnai F20 ST, FEI at WinTech Nano-Technology Services Pte. Ltd., Singapore. The TEM operated at 200 keV with a point to point of 0.24 nm and a camera length of 100 mm. TEM is used to analyze selected area diffraction (SAD) pattern, high-resolution imaging (HRTEM) and energy dispersive X-ray spectrometer (EDS). The diameter size for the SAD was between 280 nm to 300 nm. EBSD analysis was conducted at Bruker Singapore Pte. Ltd. by using an e-Flash Bruker detector attached to a ZEISS scanning electron microscope (SEM). For EBSD analysis, a very fine, flat polished surface was required where the specimen preparation procedure was similar to the specimen preparation for scanning electron microscope (SEM) analysis; an ion milling was performed after fine polishing to obtain a smoother surface. D5000 Siemens X-ray diffraction equipment was used to conduct XRD analysis at room temperature. The XRD analysis machine employed a monochromatic X-ray source of CuK\(\alpha\) radiation, where \(\lambda\) = 1.5406 A with a tube current of 30 mA and voltage of 40 kV. A range of 10\({}^{\circ}\) to 100\({}^{\circ}\) of 20 was selected with a step size of 0.05\({}^{\circ}\). The specimens for hardness test analysis were initially mechanically ground using grit 600. The specimens were then tested using the Matsuzawa-DVK II series Vickers Hardness Tester with a load of 30 kg at room temperature. Indentation tests were performed using a diamond pyramid indenter pressed in a perpendicular direction into the specimens' surface. Five indentations were performed on the surface of the specimens and the average of the hardness value was taken as the hardness value of the alloys. The specimens were prepared for the creep test by cutting the plate into a rectangular shape using electrical discharge machining (EDM). The dimensions of the specimens were in accordance with ASTM E139, as shown in Figure S1 (presented in the Supplementary Materials). To conduct a creep test, the MAYES TC 20 creep machine was used in the research, as shown in Figure S2 (presented in the Supplementary Materials). The creep machine's load and furnace temperature was calibrated by using a standard load cell and thermocouple prior to the actual creep test. The Fe-40 Ni-24 Cr alloy in plate form was initially used in the research. An EDM wire cut machine was used to cut the specimens into a rectangular form of shape. The specimens were then subjected to the heat-treatment process. In this regard, this test was conducted in a dead-load knife-edge lever creep machine with a ratio of 1:10 in a three-zone furnace.