Effects of Aluminum Content on Microstructure and Matrix Hardness of ‎Spherical Graphite Cast Irons Produced by in-Mold ‎Process

In this research, the effect of various amounts of aluminum on microstructure and ‎matrix hardness of ductile cast irons produced by in-mold casting process is investigated. ‎For this purpose, spherical graphite cast iron containing 3‎‏.‏‎7, 6‎‏.‏‎4 and 7‎‏.‏‎5 wt. % aluminum, ‎respectively, were prepared in Y-block form via in-mold process. After casting, samples ‎were prepared for microstructural studies, using conventional methods, and then were ‎examined by optical and scanning electron microscopy. Chemical composition of samples ‎was determined using optical emission spectrometry (OES), X-ray fluorescence (XRF), and ‎carbon-sulfur analyzer (LECO) method. X-ray diffraction test (XRD) was used for phase ‎identification. The results indicate changing of the precipitated pearlite morphology as the ‎aluminum content increases. Also pearlite and ferrite hardness increases, 178 and 164 ‎Vickers, respectively, as a result of increasing aluminum content from 3.7 to 7.5 wt. %. ‎Increasing the number of nodular graphites from 422 to 668 per square millimeter, reducing the graphite diameter from 13.1 to 8.8 micrometers, and changing the percentage of spherical graphite from ‎‎60 to 48 percent, with increasing aluminum content, are other noteworthy results.‎