Analysis of Graphite Nuclear in Spheroidal Graphite Cast Iron and Mechanism of Nodule Count Increase by Bismuth Oxide

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Abstract

<p>In order to elucidate the mechanism of nodule count increase by Bi, we analyzed spheroidal graphite cast iron with increased nodule count by Bi addition. In the Scanning Electron Microscope - Energy Dispersive X-ray Spectrometry (SEM-EDS) analysis, Bi was identified to be present near the center of the spheroidal graphite. The center of this spherical graphite was pretreated by Focused Ion Beam (FIB) micro sampling method to prepare analytical sample and analyzed by Transmission Electron Microscope - Energy Dispersive X-ray Spectrometry (TEM-EDS). As a result, it was found that Bi exists as Bi–La–Ce–Sb oxide on the outer periphery of the graphite core centered on (MgCa) S.</p><p>To verify the effect of the Bi–La–Ce–Sb oxide on the increase in nodule count, we first used mechanical alloying to prototype a Bi–La–Ce–Sb oxide having the same composition as that observed via TEM-EDS. This oxide was then added to the molten spheroidal graphite cast iron. As a result, nodule count did not increase with the addition of the prototype Bi–La–Ce–Sb oxide alone, but when the prototype Bi–La–Ce–Sb oxide and Fe–Si inoculants were mixed and added, the nodule count increased more than when only the Fe–Si inoculants was added.</p><p>From these results, it is considered that the effect of increasing nodule count by Bi addition is that Bi acts on graphite nucleus as an oxide.</p><p> </p><p>This Paper was Originally Published in Japanese in J. JFS 91 (2019) 221–227. Some spelling errors were modified.</p>

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 62 (9), 1393-1400, 2021-09-01

    The Japan Institute of Metals and Materials

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