Influence of Cooling Rate on Nature and Morphology of Intercellular Precipitates in Si-Mo Ductile Irons

Youssef, Mervat; Nofal, Adel; Hussein, A. A.

doi:10.4028/www.scientific.net/msf.925.231

Cited by 8 publications

(5 citation statements)

References 6 publications

(12 reference statements)

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“…From this, it follows that the ambient temperature microstructure mainly consists of graphite (9.6 vol.%), ferrite (88.8 vol.%), and carbide phases (i.e., M6C [1.2 vol.%] and M7C3 [0.2 vol.%]). In fact, the real microstructure of Si-Mo ductile iron consists of a graphite nodules, ferritic metallic matrix and small percentage of pearlite plus Fe-Mo carbides in intercellular regions [9,16]. It is worth also pointing that as Thermo-Calc analysis provides estimations in equilibrium conditions, a fraction of a percent of carbides forming elements such as, e.g., Cr gave trace percentage of M7C3 in Si-Mo ductile iron.…”

Section: Solidification and Solid-state Transformationmentioning

confidence: 99%

“…Moreover, the high tendency for carbide precipitation into the cell boundaries of Si-Mo ductile iron has scarcely been dealt with in the literature. Limited data on the cooling rate-microstructure of Si-Mo ductile iron relationship (which is crucial for the formation of castings) in a wide range of wall thicknesses has been provided in [16]. Nofal [16] stated that the morphology and composition of the carbide precipitate depend on the cooling rate of the casting.…”

Section: Introductionmentioning

confidence: 99%

“…Limited data on the cooling rate-microstructure of Si-Mo ductile iron relationship (which is crucial for the formation of castings) in a wide range of wall thicknesses has been provided in [16]. Nofal [16] stated that the morphology and composition of the carbide precipitate depend on the cooling rate of the casting. Additionally, he concluded that as the cooling rate increases, the precipitate gains a lamellar structure that is typical of pearlite, while at a slower cooling rate, the precipitate gains a spheroidal or rod-like structure.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Influence of Cooling Rate on Microstructure Formation of Si–Mo Ductile Iron Castings

Górny

Kawalec

Gracz

et al. 2021

Metals

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The present study highlights the effect of the cooling rate on the microstructure formation of Si–Mo ductile iron. In this study, experiments were carried out for castings with different wall thicknesses (i.e., 3, 5, 13, and 25 mm) to achieve various cooling rates. The simulation of the cooling and solidification was performed through MAGMASOFT to correlate the cooling conditions with the microstructure. The phase diagram of the investigated alloy was calculated using Thermo-Calc, whereas the quantitative metallography analyses using scanning electron microscopy and optical microscopy were performed to describe the graphite nodules and metallic matrix morphologies. The present study provides insights into the effect of the cooling rate on the graphite nodule count, nodularity, and volumetric fractions of graphite and ferrite as well as the average ferritic grain size of thin-walled and reference Si–Mo ductile iron castings. The study shows that the cooling rates of castings vary within a wide range (27 °C–1.5 °C/s) when considering wall thicknesses of 3 to 25 mm. The results also suggest that the occurrence of pearlite and carbides are related to segregations during solidification rather than to cooling rates at the eutectoid temperature. Finally, the present study shows that the longitudinal ultrasonic wave velocity is in linear dependence with the number of graphite nodules of EN-GJS-SiMo45-6 ductile iron.

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Section: Solidification and Solid-state Transformationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of Cooling Rate on Microstructure Formation of Si–Mo Ductile Iron Castings

Górny

Kawalec

Gracz

et al. 2021

Metals

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“…Considering that the gears are the important transmission part of the reducers which can reduce the speed, increase the torque, and change the direction of power delivery, the gears in reducers are usually required to have superior mechanical performance [3,4]. Generally, ductile iron, also known as spheroidal graphite iron, become a commonly used material for gears in many reducer manufacturers, due to its low cost, high strength, and hardness [5].…”

Section: Introductionmentioning

confidence: 99%

Revealing the strength and toughness mechanisms of ductile iron in three heat‐treatment processes

Lin,

Jin,

Chen

et al. 2024

Materialwissenschaft Werkst

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Microstructural characteristics and mechanical properties of the ductile iron in three heat treatment processes (normalizing, quenching + high‐temperature tempering and isothermal quenching) were investigated in this paper. The pearlite and ferrite with large‐sized spherical graphites can be obtained in the normalized sample, and the spherical graphites with relatively large size can still be observed in the mechanical mixture of tempered martensite and acicular ferrite for the quenched‐tempered sample. Meanwhile, the lower bainite accompanied with the relatively fine spherical graphites are existed in the isothermal‐quenched sample. The difference of tensile strength is mainly caused by the phase composition, distribution and size of the spherical graphites and the effect of the solid solution strengthening. The weaker degree of the debonding damage, higher proportion of high‐angle grain boundaries will improve the impact toughness of the ductile iron. In a word, the optimum combination of strength and toughness is acquired by using isothermal quenching, and the tensile strength and impact toughness are ~1350 MPa and ~10.62 J, respectively.

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“…The microstructure of DCI strongly varies depending on the cooling rate. The experiments involving casting SiMo50-7 (C: 2.61%, Si: 5.07%, Mo: 0.7%, Mn: 0.26%, P: 0.035%, S: 0.012%, Mg: 0.037%) into green sand molds with diameters of 3 mm, 6 mm, and 9 mm resulted in evident coarsening of the spheroidal graphite and ferrite grains [ 21 ]. Simultaneously, the amount of M 6 C carbides located at original austenite boundaries and surrounding the colonies of perlite remain practically unaffected.…”

Section: Introductionmentioning

confidence: 99%

Experimental Simulation of Directional Crystallization of SiMo Cast Iron Alloyed with Al and Cr

Morgiel,

Kopyciński

2024

Materials

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SiMo ductile cast iron combines ease of part fabrication with good mechanical properties, including a usable plasticity range. Its poor corrosion resistance inherited from grey cast iron could be alleviated through alloying with Al or Cr additions capable of forming a dense oxide scale protecting the substrate. However, the presence of Al and Cr in cast iron tends to make the material brittle, and their optimum alloying additions need to be studied further. The present work was aimed at investigating the effect of crystallization rates on microstructure changes during directional crystallization of SiMo-type alloys with up to 3.5% Al and 2.4% Cr. The experiment was performed using the Bridgman–Stockbarger method. The tubular crucible was transferred from the hot section to cold section at rates ranging from 5 mm/h to 30 mm/h with a 4/5 crucible length and then quenched. The introduced Al promoted graphitization up to a point, wherein, at the highest applied addition, the graphite precipitation preceded crystallization of the rest of the melt. A rising level of Cr in these alloys from 1% to 2.4% resulted in the formation of low and high contents of pearlite, respectively. The higher crystallization rates proved effective in increasing the ferrite content at the expense of pearlite. In the investigated cast iron samples with smaller applied alloying additions, Widmanstätten ferrite or ausferrite, i.e., fine acircular phase, were often found. The switch from directional crystallization to quenching caused a transition from a liquid to solid state, which started with nucleation of islands of fine austenite dendrites with chunky graphite eutectic separating them. As these islands expanded, they pushed alloying additions to their sides, promoting carbide or pearlite formation in these places and forming a super-cell-like structure. The performed experiments helped gather information concerning the sensitivity of the microstructure of SiMo cast iron modified with Al and Cr to crystallization rates prevailing in heavy cast structures.

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Influence of Cooling Rate on Nature and Morphology of Intercellular Precipitates in Si-Mo Ductile Irons

Cited by 8 publications

References 6 publications

Influence of Cooling Rate on Microstructure Formation of Si–Mo Ductile Iron Castings

Influence of Cooling Rate on Microstructure Formation of Si–Mo Ductile Iron Castings

Revealing the strength and toughness mechanisms of ductile iron in three heat‐treatment processes

Experimental Simulation of Directional Crystallization of SiMo Cast Iron Alloyed with Al and Cr

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