PSI - Issue 59

Teguh Muttaqie et al. / Procedia Structural Integrity 59 (2024) 222–229 Muttaqie et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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5.3. Post-test observation Figure 6 shows the metallographic examination of the impact specimen using aqua regia chemical for etching. This metallography characterization was performed using a metallography microscope. This observation shows that SUS 304 is austenitic steel that is suitable for low temperatures. However, the image captures a typical characteristic of plastic fracture, indicating that there is no ductile-brittle transformation in the test specimen.

Zone 1

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Zone 3

Fig. 6. Microstructure image taken from the Charpy specimen.

The magnification on microscopic metallography also shows that the microstructure of SUS 304 is an annealing twin as per fabrication. It is also clearly shown that the stress crack at the impact zone and notch rupture zone are defined as transgranular fracture which occurs at lower temperature because at lower temperature grain boundaries are stronger than grains itself whereas intergranular fracture occurs generally at higher temperature because at higher temperature grain boundaries are weaker regions. 6. Conclusions The behavior of SUS 304 stainless steel under cryogenic temperatures was studied using the V-notch Charpy impact test. The analysis of impact energy from room temperature to cryogenic service temperature was also conducted along with previous test results. In addition, microstructure observation after rupture was also performed The conclusions are summarized below. In the temperature range studied, the impact energy showed a relatively linear behavior with temperature. As the temperature decreases, the material becomes more brittle, causing the rupture energy to decrease. The observed impact energy of 304 stainless steel has been modeled successfully using a