The precipitation of AlN is investigated in the austenite region of ultra low carbon steel. The evolution of the size and the morphology of AlN precipitates are studied by transmission electron microscopy (TEM) after isothermal annealing for different times at temperatures of 950 °C and 1050 °C. Various different morphologies are observed, including cuboids, large plates as well as irregular structures. In addition to the experimental analysis, thermo‐kinetic simulations are carried out with the software package MatCalc. The numerically calculated evolution of the mean radii as well as the time‐temperature‐precipitation (TTP) diagram for AlN precipitation in the present alloy show good agreement with experiment.
In this paper, the kinetics of TiN, V(C,N)) and AlN precipitation in microalloyed steel during continuous casting is investigated experimentally and theoretically. The precipitate phase fraction, mean radius, number density and composition are simulated with the thermo‐kinetic software MatCalc and compared with experimental results obtained from transmission electron microscopy analysis. A new methodology for modelling precipitation in cast steel is proposed, which consists of two parts: First, a Scheil – Gulliver simulation, which is carried out to obtain information on the amount of microsegregation during solidification. Then, based on this information, two precipitation kinetics simulations are performed: One with the chemical composition representative for the solute‐poor core of the secondary dendrite arms, the other with the composition of the residual liquid at a fraction of 5%, corresponding to the segregated solute‐rich interdendritic regions. The results of the computer simulations using the new methodology are in good agreement with experimental observation.
The present work describes the analysis of carbo‐nitride precipitation kinetics in tempered martensite of Nb–Ti‐microalloyed steel with a carbon content of 0.3 wt%. Based on the information obtained from transmission electron microscopy and scanning electron microscopy, a computational simulation procedure is developed within the software package MatCalc, which is capable of describing the experimental results in terms of the number density, composition, and type of precipitate phases. No explicit fitting parameters are used in the computer simulation. The input data is entirely based on independent physical or microstructural parameters. To determine the chemical composition and type of precipitates, energy dispersive X‐ray spectroscopy and selected area electron diffraction are utilized. The simulation results and the experimentally obtained information are in good agreement.
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