On the growth of graphite lamellae in a high Si GG20 cast iron
André Paulo Tschiptschin, Wilson Luiz Guesser
Resumo
In this paper, observations are made on the faceted crystallographic lateral growth structure of graphite flakes in a high Si GG20 cast iron. A 3.82 wt.% Si, 3.25% wt.%C slightly hypereutectic cast iron with large type C graphite flakes embedded in a ferrite + spheroidized pearlite matrix failed catastrophically. Fracture is propagated by debonding the graphite flakes from the metallic matrix, exposing the graphite flakes’ lateral surfaces on the fracture surface. Flake morphology and substructure were observed using scanning electron microscopy (SEM). Very thin and flexible triangular layers, nucleating on a “hexagonal rosette” center point, suggest a growth mechanism involving the incorporation of new carbon add-atoms. Epitaxial precipitation of secondary graphite during solid-state transformation shows a preferred growth habit in the a-direction, producing 2-D sheets of graphene to which carbon atoms can easily attach. Furthermore, the spiral growth of individual sheets, contributing to the thickening of the flake in the c-direction, could be inferred. The results are discussed, considering that graphite crystalline defects may play a decisive role in the spiral growth mechanism and the thickening of the graphite flake during solid-state secondary graphite precipitation.
Palavras-chave
References
1 Cooper CA, Young RJ, Elliott R. Cast iron: a natural metal matrix composite. In: Proceedings of the ICCM Conference; Paris; 1999 July 5-9. Tours, France: ICCM; 1999.
2 Delhaes P. Graphite and precursors. Boca Raton: CRC Press; 2001.
3 Dresselhaus MS, Dresselhaus G, Surihara K, Spain IL, Goldberg IL. Graphite fibers and filaments. Berlin: Springer; 1988. (Springer Series in Materials Science; no. 5).
4 Amini S, Abbaschian R. Nucleation and growth kinetics of graphene layers from a molten phase. Carbon 2013;51:110-123.
5 Stefanescu DM, Alonso G, Larrañaga P, De la Fuente E, Suarez R. On the crystallization of graphite from liquid iron carbon silicon melts. Acta Materialia. 2016;107(1):102-126.
6 Minkoff I, Lux B. Graphite growth from metallic solution. In: Lux B, Minkoff I, Mollard F, editors. The metallurgy of cast iron. St. Saphorin, Switzerland: Georgi Publishing; 1975. p. 473-493.
7 Stefanescu DM, Alonso G. Suarez R. Recent developments in understanding nucleation and crystallization of spheroidal graphite in iron-carbon-silicon alloys. Metals. 2020;10(4):471.
8 Stefanescu DM, Lacaze J. Thermodynamics principles as applied to cast iron. In: ASM International. ASM Handbook. 1A Cast Iron Science and Technology. West Conshohocken: ASM International; 2017.
9 Andersson JO, Helander T, Höglund L, Shi PF, Sundman B. Thermo-calc and DICTRA version 2019a. Computational tools for materials science. Calphad. 2002;26(2):273-312.
10 López M, Massone JM. Boeri RE. Evolution of the macrostructure of gray cast iron from eutectic to hypereutectic composition. Materials Science Forum. 2018;925:110-117. https://doi.org/10.4028/www.scientific.net/ MSF.925.110.
11 ASTM International. ASTM A247-19 - Standard Test Method for Evaluating the Microstructure of Graphite in Iron Castings. West Conshohocken: ASTM International; 2019.
12 Bradley WL, Srinivasan MN. Fracture and fracture toughness of cast irons. International Materials Reviews. 1990;35:139.
13 Diószegi A. Jönköping, SE: Jönköping University; 2022. Personal communication.
14 Kvasnistsa VN, Yatsenko VG, Jaszczak JA. Disclinations in unusual graphite crystals from anorthosites of Ukraine. The Canadian Mineralogist. 1999;37(4):951-960.
15 Yao Y, Wong CP. Monolayer graphene growth using additional etching process in atmospheric pressure chemical vapor deposition. Carbon. 2012;50(14):5203-5209.
16 Double DD, Hellawell A. The nucleation and growth of graphite—the modification of cast iron. Acta Metallurgica et Materialia. 1995;46(6):2435-2442.
Submitted date:
09/15/2021
Accepted date:
06/02/2022
Facebook
Google+
Twitter
LinkedIn
Mendeley
StumbleUpon
CiteULike
Reddit
Email