@article{LandesbergerKoosHofmannetal.2020, author = {Landesberger, Martin and Koos, Robert and Hofmann, Michael and Li, Xiaohu and Boll, Torben and Petry, Winfried and Volk, Wolfram}, title = {Phase Transition Kinetics in Austempered Ductile Iron (ADI) with Regard to Mo Content}, volume = {13}, pages = {5266}, journal = {Materials}, number = {22}, publisher = {MDPI}, address = {Basel}, issn = {1996-1944}, doi = {https://doi.org/10.3390/ma13225266}, year = {2020}, abstract = {The phase transformation to ausferrite during austempered ductile iron (ADI) heat treatment can be significantly influenced by the alloying element Mo. Utilizing neutron diffraction, the phase transformation from austenite to ausferrite was monitored in-situ during the heat treatment. In addition to the phase volume fractions, the carbon enrichment of retained austenite was investigated. The results from neutron diffraction were compared to the macroscopic length change from dilatometer measurements. They show that the dilatometer data are only of limited use for the investigation of ausferrite formation. However, they allow deriving the time of maximum carbon accumulation in the retained austenite. In addition, the transformation of austenite during ausferritization was investigated using metallographic methods. Finally, the distribution of the alloying elements in the vicinity of the austenite/ferrite interface zone was shown by atom probe tomography (APT) measurements. C and Mn were enriched within the interface, while Si concentration was reduced. The Mo concentration in ferrite, interface and austentite stayed at the same level. The delay of austenite decay during Stage II reaction caused by Mo was studied in detail at 400 °C for the initial material as well as for 0.25 mass \% and 0.50 mass \% Mo additions.}, language = {en} } @article{LiHofmannLandesbergeretal.2021, author = {Li, Xiaohu and Hofmann, Michael and Landesberger, Martin and Reiberg, Marius and Zhang, Xiao and Huang, Yuanding and Wang, Lijiu and Werner, Ewald and Gan, Weimin}, title = {A Unique Quenching and Deformation Dilatometer for Combined In Situ Neutron Diffraction Analysis of Engineering Materials}, volume = {23}, pages = {2100163}, journal = {Advanced Engineering Materials}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1527-2648}, doi = {https://doi.org/10.1002/adem.202100163}, year = {2021}, abstract = {A modified quenching and deformation dilatometer (TA instruments DIL 805A/D/T) is now in operation at the Heinz Maier-Leibnitz Zentrum (MLZ, Germany) neutron center. It is customized for running neutron scattering measurements during the temperature/deformation treatment of the sample, in particular neutron diffraction (phase, texture, and lattice strain) and neutron small angle scattering. The bulk length change of dilatometer specimens is successfully combined with in situ neutron diffraction patterns for analyzing dynamic processes in metallic materials. A detailed introduction to the unique dilatometer is given and examples of recent experiments highlight the use of the added insight provided by combining diffraction and dilatometry.}, language = {en} } @article{LiWagnerStarketal.2019, author = {Li, Xiaohu and Wagner, Julia N. and Stark, Andreas and Koos, Robert and Landesberger, Martin and Hofmann, Michael and Fan, Guohua and Gan, Weimin and Petry, Winfried}, title = {Carbon Redistribution Process in Austempered Ductile Iron (ADI) During Heat Treatment—APT and Synchrotron Diffraction Study}, volume = {9}, pages = {789}, journal = {Metals}, number = {7}, publisher = {MDPI}, address = {Basel}, issn = {2075-4701}, doi = {https://doi.org/10.3390/met9070789}, year = {2019}, abstract = {In-situ synchrotron diffraction and atom probe tomography (APT) have been used to study the carbon diffusion and redistribution process in austempered ductile iron (ADI) during austempering. The process of carbon content change in bainitic ferrite during different austempering temperatures has been determined quantitatively. The transformation in ADI is controlled by decarburization of supersaturated ferrite and carbide precipitation and has been found to be divided into three stages based on a model developed for bainitic steels by Takahashi and Bhadeshia. The formation, morphology and composition of carbides and carbon clusters in ferrite after austempering have been identified unequivocally by APT. Finally, the relationships of carbon content in ferrite, carbon gap values, and austempering temperatures in the ADI alloy were expressed using empirical equations.}, language = {en} } @article{LiSaalGanetal.2016, author = {Li, Xiaohu and Saal, P. and Gan, Weimin and Landesberger, Martin and Hoelzel, Markus and Hofmann, Michael}, title = {Strain Induced Martensitic Transformation in Austempered Ductile Iron (ADI)}, volume = {746}, pages = {012055}, journal = {Journal of Physics: Conference Series}, publisher = {IOP Publishing}, address = {Bristol}, issn = {1742-6588}, doi = {https://doi.org/10.1088/1742-6596/746/1/012055}, year = {2016}, abstract = {The strain induced martensitic transformation in austempered ductile iron (ADI) has been investigated using high resolution neutron diffraction on samples compressed ex-situ to different plastic strains. In addition bulk texture measurements using neutron diffraction have been performed to calculate the orientation distribution of ferrite and austenite phases for different strain levels. Combing the detailed texture information with neutron diffraction pattern proved to be essential for quantitative phase analysis and extraction of martensite phase fractions. The martensite content induced by strain in ADI depends on austempering temperature and degree of deformation.}, language = {en} }