Metallurgical Engineering

Metallurgical Engineering

Effect of cooling rate on the microstructure and graphite morphology in the ductile iron-steel hollow sphere syntactic foams

Document Type : Research Paper

Authors
Hamid Sazegaran 1
Masoud Pour 2
milad Hojati 3
1 Department of Industrial Engineering, Faculty of Engineering, Quchan University of Advanced Technology,
2 Department of Mechanical Engineering, Faculty of Engineering, Quchan University of Advanced Technology
3 Production Management of Mashhad Powder Metallurgy Company (
10.22076/me.2017.40715.1059
Abstract
In this study, ductile iron-steel hollow sphere syntactic foams were manufactured using sand mold casting technique. The steel hollow spheres were synthesized through fluidized bed and in this process, commercial iron powder was coated on the expanded polystyrene spheres. After coating, De-bonding and sintering processes were carried out and the steel hollow sphere produced with 4, 6, and 8 mm in diameter. Then, the steel hollow spheres were randomly filed in the cavities of prepared mold and ductile iron infiltrated the interstitial space between the spheres. Thus, ductile iron- steel hollow sphere syntactic foams with 4, 6, and 8 mm spheres sizes. Microstructural properties of manufactured foams were investigated by optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). In addition, cooling rates in the syntactic foams with different sphere sizes were calculated and effects of cooling rate on the graphite morphology and microstructure were studied. The results revealed that decreasing the spheres size caused to increasing the cooling rate. Furthermore, by increasing the cooling rate, surface fraction of graphite, graphite circularity, and surface fraction of iron carbide decrease and graphite nodule count increases.
Keywords: Syntactic foam, Ductile iron, Steel hollow sphere, Casting, Scanning electron microscopy.
Keywords
Syntactic foam
ductile iron
Steel hollow sphere
Casting
Scanning electron microscopy
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  • Receive Date 20 March 2016