PSI - Issue 71

Sameer S. Gajmal et al. / Procedia Structural Integrity 71 (2025) 430–437

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3.2 Porosity Fraction Porosity fraction was calculated by using a Four-Dimensional X-ray microscope (FDXRM) facility (Make: Zeiss, Model: X Radia Versa 520). The vacant spaces present in the material is termed as porosity or void fraction and accordingly it is expressed and measured as the ratio of voids volume to total volume of the material, Diószegi et al. (2015) Casting porosity can be due to either variation in the temperature and humidity or gasification of impurities at molten metal temperatures. The ideal density of material is always greater than its porous structure. The measurements through FDXRM of microwave casted specimens are shown in Figs. 7(a) and 7(b) and similarly the FDXRM measurements of conventional castings are shown in Figs. 8(a) and 8(b)

Fig. 7 (a). FDXRM images of Microwave Cast Specimens at 100 μm

Fig. 8 (a). FDXRM images of Conventional Cast Specimens at 100 μm

Fig. 7 (b). FDXRM images of Microwave Cast Specimens at 100 μm

Fig. 8 (b). FDXRM images of Conventional Cast Specimens at 100 μm

4. Results and discussion 4.1 Solid Shrinkage Analysis

All 18 nos. of samples are measured for the solid shrinkage using a screw gauge micrometer having a least count of ±1 µm and the readings are summarized in Table 4. Shrinkage was measured at the diameter of the specimen at top, middle and at the bottom. Table 4 and Table 6 show the solid shrinkages of the microwave specimens. Table 5 and Table 7 show the solid shrinkages of the conventional specimens. Table 8 shows the summary of solid shrinkage. It is observed that the average % solid shrinkage in case of conventional pin castings is 32.88 % more as compared to the average % solid shrinkage of microwave cast specimens. Table 4 – Microwave Cast Specimen – Average Shrinkage Value Calculation Microwave Cast Specimen Position Dia. as per Drawing (mm) Dia. of Cast Specimen (mm) % Shrinkage Specimen 1 Top 17.00 16.46 3.18 Middle 16.75 16.28 2.81 Bottom 16.50 15.96 |3.27 Specimen 2 Top 17.00 16.48 3.05 Middle 16.75 16.30 2.75 Bottom 16.50 15.98 3.20 Specimen 3 Top 17.00 16.47 3.10 Middle 16.75 16.31 2.70 Bottom 16.50 15.99 3.10