Papers by Keyword: Austempering

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Authors: Esa Vuorinen, Xiang Chen
Abstract: The in-situ X-ray diffraction observations of the bainitic transformation of silicon alloyed steels were performed using the high temperature X-ray diffraction technique. The experimental results have shown that the volume fraction and carbon content of austenite remains a constant value which indicate that the transformation is almost finished after the early stages of austempering transformation. Asymmetry diffraction peaks are obtained for samples at the early stage of transformation due to a heterogeneous distribution of carbon in different regions of austenite and thus exists two types of austenite: low-carbon austenite (γLC) and the high-carbon austenite (γHC). The experimental results supports that the bainite growth is by a non-diffusive mechanism when austempering temperature is in the lower bainite transformation temperature.
Authors: Susil K. Putatunda, Jiang Huai Yang
Authors: K. Thillairajan, V. Balusamy, V. Ramaswamy
Abstract: An attempt has been made in this research work to develop strong and tough bainitic steels in shorter transformation durations of less than three hours leading to ease of production for steel industries making these steels. High carbon medium alloy steel with high amounts of silicon, cobalt and aluminum was taken up for this study. The steel samples were austempered at 473, 523, 573, and 623K for 30, 45, 60, 90, 120, 150, and 180 minutes and then characterized by optical metallography, scanning electron microscopy, transmission electron microscopy and X-ray diffraction investigations. Microstructure containing plates of bainitic ferrite and substantial amounts of retained austenite placed in between the bainitic ferrite laths was produced. The steel after austempering had hardness in the range 450 – 720 HV at 30 kg load, tensile strength of about 560-620 MPa and room temperature notch impact toughness of about 10J with very less ductility. The details of alloy design and making, metallurgical and mechanical characterizations are discussed.
Authors: M.M. Cisneros-Guerrero, R.E. Campos-Cambranis, M. Castro-Román, M.J. Pérez-López
Authors: De Qun Kong, Qing Suo Liu, Zhan Ji Dong
Abstract: The growth behavior of the bainite obtained by short-time isothermal transformation at 200°C in the high carbon silicon-containing steel has been investigated. It is found that the bainite appears the plates consisting of single ferrite phase, and that both the lateral growth and longitudinal growth of bainite have weak ability to traverse the lattice-distortion strain fields and grain interface of austenite.
Authors: Li Wang, T.Y. Hsu
Abstract: Transformation-induced-plasticity (TRIP) –aided steels are a promising solution for producing lighter, crash-resistant car bodies, due to their high-strength and large uniform elongation. The influences of the austempering temperature and time on the microstructure mechanical properties and the transformation behavior of a Si-Mn TRIP steel are investigated in this paper.
Authors: Jin Hai Liu, Guo Lu Li, Xue Bo Zhao, Xiao Yan Hao, Jian Jun Zhang
Abstract: The microstructure and properties of austempered ductile iron with carbides was studied to increase the abrasive resistance of ADI. It was proven that the austempering temperature influences greatly the microstructure, impact toughness, hardness and abrasion resistance of CADI. With increase of austempering temperature, the acicular ferrite becomes thicker and bigger, the impact toughness rises, and the hardness decreases. But there is a complicated effect of austempering temperature on wet abrasion resistance. In addition, the CADI grinding balls were cast and the field testing was performed. The CADI ball is one third of abrasion loss of low chromium cast iron, zero rate of breakage and no loosing round.
Authors: R. Prem Kumar, S.S. Mohamed Nazirudeen, J. Anburaj
Abstract: Carbidic Austempered Ductile Iron (CADI) is a recent addition to the Austempered Ductile Iron (ADI) family. The effect of chills on the microstructure and mechanical properties of CADI was investigated after Austempering. Three samples of chromium alloyed CADI, the first sample without chill, the second sample with bottom chill and the third sample with bottom and side chills were produced in order to evaluate the effect of chills on its mechanical properties. The samples were austenised for 2 hours at 925° C and then austempered at 325° C for 2 hours in a salt bath furnace. The microstructural features of the as-cast and the austempered CADI samples were analysed using Optical Microscope and Scanning Electron Microscope (SEM). The mechanical properties of the CADI samples (as-cast and austempered) were evaluated for hardness, impact and wear. By austempering at 325° C for 2 hours a typical microstructure of bainite was produced in all the three samples. Hardness and wear resistance of austempered samples produced using bottom and side chills were considerably higher than the corresponding values in samples produced without using any chill and also by using only bottom chill. This enhanced mechanical property in the bottom and side chill sample is attributed to the presence of bainite, carbides and more of uniform fine graphite nodules.
Authors: Mohamed Soliman, Adel A. Nofal, Heinz Palkowski
Abstract: Three ductile irons with different aluminum-and manganese-content were subjected to two thermo-mechanical schedules. In the first schedule, a total deformation of φt = 0.3 is applied on the ductile irons in the austenitic region before the austempering process. In the second schedule, the materials are subjected to deformation of 0.2 in the austenitic region and deformation of 0.1 during austempering (ausforming). Mechanical deformation of austenite prior to the transformation “stage I” pronouncedly accelerated the transformation due to increasing the nucleation sites of ausferrite. This increase has its impact on enhancing the microstructural uniformity and refining the ausferrite platelets. On the other hand, the retained austenite content was not significantly affected by the applied ausforming. Remarkable increase in hardness, strength and ductility of the ausformed ductile iron due to the latter effects is observed.
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