Correlation between Microstructure and Mechanical Properties of Austempered Ductile Irons

Abstract:

Austempered ductile cast irons (ADI) have received great attention in last years because their combined properties of good ductility, high strength and fracture toughness, good fatigue strength, good wear properties and low production cost. Such combination of properties can be reached because of their microstructures consist of a mixture acicular ferrite (bainite), residual austenite with a high carbon content and nodular graphite. In this work, the effect of austempering heat treatment on the microstructure of a commercial alloy to produce three different grades of ADI, with different strength level, is analyzed. Microstructure characterization has been performed using techniques of optical microscopy, scanning electron microscopy and x-ray diffraction. Mechanical properties were evaluated from tensile and impact tests at room temperature. In addition, the residual stress due to heat treatment was evaluated. The results of this study show that there is a strong relationship between austempering temperatures and mechanical properties. The highest tensile and yield strength obtained were 1599 and 1427 MPa, respectively, for the sample austempered at 280°C. The sample austempered at 320°C presented the highest Charpy absorption energy (99,90 J) and highest volume fraction of austenite (27%).

• Periodical: Materials Science Forum (Volume 925)
• Pages: 203-209
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.925.203
• Online since: June 2018
• Authors: Vinicius Cardilo Campos Alves*, Luciano Lobo de Almeida Baracho, Césio Túlio Alves dos Santos, Luiz Carlos Rolim Lopes, Éder dos Reis Silva, Fabiane Roberta Freitas da Silva, Gláucio Soares da Fonseca, Ricardo Henriques Leal, Maria da Penha Cindra Fonseca
• Keywords: Austempered Ductile Cast Iron, Impact Strength, Residual Austenite, Residual Stress, Tensile Strength

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