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Journal ArticleDOI

Material Characterization of Austempered Ductile Iron (ADI) Produced by a Sustainable Continuous Casting–Heat Treatment Process

TL;DR: In this paper, the authors explored the new processing technology for direct manufacturing of lightweight austempered ductile iron (ADI) casting in a permanent mold, which is based on the innovative integrated approach toward casting and heat-treatment process.
Abstract: Selecting a suitable manufacturing process is one way of achieving sustainability of a product by diminishing energy consumption during its production cycle and improving material efficiency. The article attempts to explore the new processing technology for direct manufacturing of lightweight austempered ductile iron (ADI) casting in a permanent mold. The new processing technology is based on the innovative integrated approach toward casting and heat-treatment process. In this technology, the ductile iron samples obtained using the permanent mold are first austenized immediately after solidification process followed by austempering heat treatment in the fluidized bed and then air cooled at room temperature to obtain ADI material. The influence of austempering time on the microstructural characteristics, mechanical properties, and strain-hardening behavior of ADI was studied. Optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were performed to correlate the mechanical properties with microstructural characteristics. It was observed that the mechanical properties of resulting ADI samples were influenced by the microstructural transformations and varied retained austenite volume fractions obtained due to different austempering time. The results indicate that the strain-hardening behavior of the ADI material is influenced by the carbon content of retained austenite.
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Journal ArticleDOI
TL;DR: In this paper, the impact of cutting conditions on chip morphology and surface roughness is also investigated, and the experimental results revealed that the combination of low feed rate and higher cutting speed leads to higher mechanical and thermal loads on the tool's cutting edge, resulting in higher specific cutting force values.
Abstract: Dry machining is being recognized as ecological machining due to its less environmental impact and manufacturing cost. However, the choice of dry machining is mainly influenced by the workpiece material properties, machining operation and cutting conditions. The recent emergence of austempered ductile iron (ADI) can be considered a significant economic advantage to the increasing industrial demand for cost- and weight-efficient materials. However, due to its microstructure-induced inherent properties, ADI is considered hard-to-machine material. Thus, the dry drilling of ADI is investigated in this paper. The ADI material used in the present study is produced using an innovative process route for near net shape casting production. Drilling experiments are conducted on a DMU80P Deckel Maho five-axis machining centre using PVD-coated carbide tools under dry cutting environment. The dry drilling of ADI under different cutting conditions is evaluated in terms of specific cutting force and tool wear analysis. The influence of cutting conditions on chip morphology and surface roughness is also investigated. The experimental results revealed that the combination of the low feed rate and higher cutting speed leads to the higher mechanical and thermal loads on the tool's cutting edge, resulting in higher specific cutting force values. This behaviour is further supported by the chip morphology analysis, which revealed the formation of segmented chips at higher cutting speed with segment spacing increase with an increase in feed rate. Depending upon the cutting parameters, different modes of tool failures including crater wear, flank wear, chipping, breakage and built-up edge were observed. Surface roughness analysis revealed the influence of tool wear and chip morphology on the machined surface finish.

25 citations

Journal ArticleDOI
TL;DR: In this article, the authors compared the empirical Hollomon equation and the dislocation-density-related Voce equation to analyze the different strain hardening behaviors of DIs and ADIs, and found that the DIs strain-hardening behavior was mainly caused by the fine pearlitic structure, consisting of ferritic lamellae with sub-micrometric widths.

20 citations

Journal ArticleDOI
TL;DR: In this article, the authors determined a procedure based on tensile testing to assess the critical range of austempering times for having the best ausferrite produced through Austempering.
Abstract: The aim of this investigation was to determine a procedure based on tensile testing to assess the critical range of austempering times for having the best ausferrite produced through austempering. The austempered ductile iron (ADI) 1050 was quenched at different times during austempering and the quenched samples were tested in tension. The dislocation-density-related constitutive equation proposed by Estrin for materials having high density of geometrical obstacles to dislocation motion, was used to model the flow curves of the tensile tested samples. On the basis of strain hardening theory, the equation parameters were related to the microstructure of the quenched samples and were used to assess the ADI microstructure evolution during austempering. The microstructure evolution was also analysed through conventional optical microscopy, electron back-scattered diffraction technique and transmission electron microscopy. The microstructure observations resulted to be consistent with the assessment based on tensile testing, so the dislocation-density-related constitutive equation was found to be a powerful tool to characterise the evolution of the solid state transformations of austempering.

16 citations

Book ChapterDOI
06 Jan 2016

8 citations

Journal ArticleDOI
TL;DR: In this article, the physical properties of the ausferritic as-cast materials were characterized and an experimental model was developed to define the optimal processing parameters of castings presenting different thermal moduli, in terms of chemical composition, temperatures and time parameters.
Abstract: In previous studies, the process parameters to obtain ausferritic ductile iron in as-cast conditions by means of engineered cooling were defined, that is, without an austempering heat treatment. This material was fundamentally characterized, and its mechanical properties were determined. It was demonstrated that obtaining fully ausferritic microstructures by means of engineered cooling was feasible and that the properties met the requirements of the conventionally produced austempered ductile iron. Additionally, an experimental model was developed to define the optimal processing parameters of castings presenting different thermal moduli, in terms of chemical composition, temperatures and time parameters. The aim of the present work is to go into detail about the physical properties of the ausferritic as-cast materials. The chemical composition of the samples was defined by means of the experimental model. The isothermal transformation temperature was changed from 300 to 400 °C, while the other process parameters (shakeout temperature and isothermal transformation time) remained constant. Due to the excellent strength/toughness ratio of these materials, they are prone to being used on different applications such as automotive suspension components, rail components in low temperature environments and pumps and engines exposed to corrosive marine conditions among others. With the aim of responding to this demand, an advanced characterization of the material’s low temperature, corrosion or dynamic properties was performed on this work. These results were compared to the conventionally heat-treated austempered ductile iron as well as other nodular iron ferritic–pearlitic grades found in the literature.

7 citations

References
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Book
01 Dec 2001

104 citations

Journal ArticleDOI
TL;DR: In this paper, a nodular or ductile cast iron with predominantly pearlitic as-cast structure was processed by a novel two-step austempering process, which resulted in significant improvement in yield and tensile strengths and fracture toughness of the material over the conventional single-step Austempering Process.

103 citations

Journal ArticleDOI
TL;DR: In this article, the results of machining tests carried out to determine the effect of microstructure and mechanical properties of austempered ductile irons (ADIs) on cutting forces and surface roughness were presented.

81 citations

Journal ArticleDOI
TL;DR: In this article, the filling and solidification of a casting of an automotive piston produced from an aluminum alloy was modeled by using the volume-of-fluid method, and the model provided a solution of acceptable accuracy despite some uncertainty in material properties and boundary and initial conditions.

80 citations