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Volume 6 Research & Reviews: Journal of Material Sciences MatSciEngg 2018
October 15-17, 2018
October 15-17, 2018 Helsinki, Finland
31st Materials Science and Engineering
Conference: Advancement & Innovations
Effect of degeneracy in graphite particle aspect ratio (AR) on some mechanical properties of as-cast
spheroidal graphite iron (SGI)-compacted graphite iron (CGI) cast iron series
Benjamin I Imasogie
Obafemi Awolowo University, Nigeria
Statement of the Problem: Spheroidal Graphite Iron (SGI) and Compacted Graphite Iron (CGI) castings and their derivatives
have proven to be the cost-effective materials of choice and/or potential alternatives to other conventional/competing materials
(e.g. malleable iron, steel, aluminum, etc., castings) andmanufacturing processes (forging, machining, fabrication, etc.) inmany
automotive and industrial applications, with either an outright improvement in service performance or lower production cost
or both. The general properties of this set of engineering purpose cast irons (often used as-cast) depend largely on the relative
amount, distribution, structure and morphology of the characteristic graphite component, thus impacting significant measure
of ductility in the system. Chemistry and processing of the melt dictate both the desirable graphite structure/morphology and
the matrix structure during solidification. However, occasionally, consistent and uniquely spheroidal or compacted form-
types of graphite required, are not readily obtained in regular production of these irons. This may result from insufficient or
excessive melt treatment, choice and mode of addition of the graphite nodularising treatment agent, non-uniform treatment
or the presence of inhibiting elements.
Methodology &Theoretical Orientation: A range of un-alloyed SGI-CGI iron grades were produced in a series of systematic
iron-melt treatments with a special Ca-CaC2-Mg master alloy. Data sets are presented and analyzed to gauge the effect of
variation in graphite particle Aspect Ratio (AR) range in an as-cast SGI-CGI iron series ranging from ASTM type I (fully
spheroidal) to ASTM types II-III-IV (mixture of spheroidal and compacted/vermicular graphite forms) on some of their
selected mechanical properties.
Findings: It was observed that generally, properties relating to strength and ductility progressively decrease as the proportion
of non-nodular graphite (AR≤0.65) increases. In particular, properties relating to failure (tensile and fatigue strengths) are
more affected by small amounts of such irregular graphite forms than properties (proof strength, etc.) not involving failure.
Conclusion & Significance: This research has established that in general, the level of graphite spheroidization or nodularization
(as measured by the graphite particle AR), plays a significant role in determining the resulting mechanical properties in the
SGI-CGI family spectrum. Conversely, increasing amounts of non-spheroidal graphite particles, either in the compacted or
degenerate form (vermicular) caused progressive reductions in tensile and yield strengths, ductility (% elongation), notch
impact values, fatigue limit and modulus of elasticity. Thus, the level of graphite spheroidization in either the optimum SGI
or CGI is critical to its consideration for applications in functional components in automobile, heavy machinery, etc. and in
applications where some degree of toughness is required.
Biography
Benjamin I Imasogie has special interest and expertise in the development and characterization of ductile iron; DI (also known as spheroidal (SGI) or nodular
graphite iron (NGI), Austempered Ductile Iron (ADI) and nanostructured (LIGA-Ni-Fe MEMS) engineering materials. He has written and presented several scholarly
papers on these topics in high impact materials science and engineering journals such as MST, SJM, JMEPEG-ASM, Materials Performance (MP), JMMCE, ACMM,
MEJ, NJMSE, Acta Materialia, Metall. and Matls. Trans., Mater. Sci. and Engg. A, etc. With respect to the pertinent paper, he is the Author of the special resource
material. He is the current Dean, Faculty of Technology, Obafemi Awolowo University, Ile-Ife, Nigeria. He is a Professor of Materials Engineering in this renowned
University. He is a Fellow of the Nigerian Society of Engineers (FNSE) and the Nigerian Metallurgical Society (FNMS).
Benjamin I Imasogie, Res. Rev. J Mat. Sci. 2018, Volume 6
DOI: 10.4172/2321-6212-C5-027