Effect of Initial Microstructure on the Activation Energy of Second Stage During Austempering of Ductile Iron

Campos-Cambranis, R.E.; Narváez, L.; Cisneros-Guerrero, M.M; Pérez-López, María Juana

doi:10.1016/s1359-6462(98)00036-0

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…As seen through Figures 9, 10 and 11, for the same austempering time, the higher the percentage of retained austenite, the smaller amount of acicular ferrite, the harder This result is also a consequence of the higher activation energy for the formation of inferior ausferrite compared to the superior ausferrite, as mentioned by Campos-Cambranis et al 24 , which leads to an increase in the percentage of retained austenite with an increase in the treatment temperature for the same time.…”

Section: Hardness Testmentioning

confidence: 64%

Microstructural Evaluation of an Austempered Cast Iron Alloy

et al. 2022

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ADI are the result of graphite nodules and ausferrite microstructure (acicular ferrite + retained austenite). Over the past few years, ADI has become an important material for engineering due to its excellent mechanical properties (outstanding ductility, high mechanical strength and good toughness) and low cost. It is known the discussion of process variables such as austempering time and temperature are extremely important for the microstructural and hardness study of these materials. Thus, in the present work, ADI cast iron was investigated under twelve different austenitic conditions, aiming to characterize the influence of the amount of austenite on the ferritic matrix on the mechanical property of hardness. The heat treatment parameters vary from three different times (40 min, 90 min and 180 min) under four temperatures (280ºC, 300 ºC, 320 ºC and 370ºC). Results show there is a decreasing of hardness linked to the increasing of retained austenite % volume. The greater amount of retained austenite % volume in the matrix was presented by sample A14, treated during 40 minutes under 370ºC and presenting 32.30% of this microconstituint. The amounts of each phase present in the studied materials were raised by quantitative metallography through the software Fiji-ImageJ, allowing a comparison of the results obtained by these two methods. Time differences on the austempering heating treatment did not show several implications on ADI microstructure. In addition, analyzes of the graphite nodules were performed.

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Section: Hardness Testmentioning

confidence: 64%

Microstructural Evaluation of an Austempered Cast Iron Alloy

et al. 2022

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“…they do not form a "branched" network. This corresponds to a mechanism in which platelets, sub-units of ferrite which are not visible individually in micrographs of Figure 4, would nucleate close to the primary sheaf and successive platelets would extend the sheaf until it impinges another sheaf [15,17,18]. The primary sheaves tend to be in contact with, or closely approach, the austenite grain boundaries and in some cases span the whole grain.…”

Section: Characterization Of Austempered Samplesmentioning

confidence: 96%

Influence of casting heterogeneities on microstructure and mechanical properties of austempered ductile iron (ADI)

2017

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An investigation was carried out to examine the influence of as-cast heterogeneities on the resulting microstructure and mechanical properties of an austempered ductile cast iron (ADI). A commercial hypereutectic ductile iron alloy with 3.59% C, 2.68% Si, 0.24% Mn and 0.46% Cu (in wt. %) was produced in a coreless induction furnace. The specimens were obtained by casting the alloy into Y-block molds. The austempering heat treatments consisted of pre-heating at 500°C, followed by austenitizing step at 900°C and 930°C during 60 minutes. Austempering was carried out in molten metal baths at temperatures of 300°C and 370°C for 30 minutes. Microstructural characterization was carried out by light optical microscopy (LOM) with image analysis, scanning electron microscopy (SEM-FEG) and X-ray diffraction with Rietveld refinement. The mechanical properties were evaluated by tensile and Vickers hardness tests. The results of this investigation indicate that as-cast heterogeneities have a detrimental effect on the transformed microstructure and mechanical properties of ADI. During austempering, non uniform distribution of graphite nodules and segregation of alloying elements at cell boundaries resulted in transformation gradients throughout the metallic matrix. Intercellular regions displayed inhomogeneous microstructures containing eutectic carbides and martensite. Yield strength, tensile strength and hardness decrease for increasing austempering temperature. Fracture surfaces showed a rapid transition from ductile to cleavage mode at intercellular regions, containing solidification carbides.

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“…A escolha da temperatura de austêmpera determinará o grau de propriedades mecânicas que o material terá, ou seja, baixas temperaturas de austêmpera (T A ≤ 350 ºC) produzirão maiores valores de resistência mecânica, limite de escoamento e dureza. Por outro lado, altas temperaturas de austêmpera, produzirão maiores valores de alongamento, energia absorvida ao impacto e resistência à fadiga (Hayrynen, 2002;Carmo, 2001;Hayrynen, 1995;Campos-Cambranis, 1998).…”

Section: Introductionunclassified

Austempering Heat Treatment Study of Cast Ductile Iron: Analysis of Mechanical and Microstructural Properties, According to the A897m Standard Specifications for Austempered Ductile Iron Castings

Schifino¹,

Sant'Anna²,

Trindade³

2018

PTQ

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The objective of this work was to develop heat treatment parameters of an austempered cast iron alloy ASTM 897 / A 897M - 1400/1100/1, aiming at the production of a truck spring support. The austempered nodular cast iron, known by the acronym ADI - Austempered Ductile Iron - is a class of nodular cast iron that, after austempered thermal treatment, increases significantly its mechanical properties and tenacity (Machado, 2007). Mechanical and metallographic tests demonstrated the great influence that the level of microshrinkage has on the elongation and mechanical resistance of the material. Generally, tensile tests demonstrate high elongation due to minimal presence of microshrinkage and segregations in the metallic matrix of the material, as well as to the presence of austenite with high carbon retained in the ADI matrix. Analyzes were performed to determine if the mechanical properties required by ASTM 897 / A897M were achieved. Within this standard, four degrees can be obtained. The degree of interest in this study was 1400/1100/1, which is the grade requested by the company, so that the truck spring support can be put into service. Tensile, Charpy and optical microscopy tests were carried out.

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Effect of Initial Microstructure on the Activation Energy of Second Stage During Austempering of Ductile Iron

Cited by 5 publications

References 5 publications

Microstructural Evaluation of an Austempered Cast Iron Alloy

Microstructural Evaluation of an Austempered Cast Iron Alloy

Influence of casting heterogeneities on microstructure and mechanical properties of austempered ductile iron (ADI)

Austempering Heat Treatment Study of Cast Ductile Iron: Analysis of Mechanical and Microstructural Properties, According to the A897m Standard Specifications for Austempered Ductile Iron Castings

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