The formation of microstructure at the center zone.
Description
The microstructure analysis process associated with this research was carried out on the surface and the center zone. The microstructure found in the center zone for all samples as has been given the codes S1, S2, S3, and S4 (Table 2) shows that graphite nodules are uniformly and roundly formed, with a ferrite and perlite structure phase, as shown in Fig. 4. This graphite structure is under the specifications of the nodular cast iron material according to the ASTM A 536 standard which is carried out through an inoculation process. In this nodularization process, magnesium (Mg) alloy elements will be added to get a round of the graphite nodule so that the ductile iron base material can withstand tensile loads and impact loads according to research Yamamoto S et al and Sasaki et al. [32, 33].
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2.3.1 The microstructure analysis procedure The microstructure analysis is based on the ASTM 247 procedure, using an Olympus BX41M optical microscope. After cutting, the specimen is polished with sandpaper (400, 800, 1500, and 2000), then etched with Nital 98mL ethanol and 2mL nitric acid (HNO3) based on the test guide on ASM Handbook Vol. 9 [28]. The sample is cut without being exposed to high heat. Furthermore, the sample size for the microstructure analysis and microhardness Vickers test is 10 x 10 x 6mm [29, 30]. The test point areas taken from each Y-Block specimen (S1, S2, S3, and S4) are four (D1, D2, D3, and D4) and are cut in different areas as shown in Fig 3a. These points are carried out on two sides, namely right site A and left site B, and each zone for each test sample has 9 test points, as shown in Fig. 3b. Figure 3b shows that there are three group test focus locations, and each has three points.