The effect of intercritical deformation on development of microstructure in low-silicon contents multiphase TRIP-assisted steels were investigated by laboratory simulation of controlled-thermomechanical processing in an automated hot compression testing machine. A typical multiple cooling stages TMP program was applied and samples were deformed in intercritical region to different strains. Microstructures of samples were characterized by optical and scanning electron microscopy, XRD and Mössbauer. The result indicated that intercritical straining increases volume fraction of polygonal ferrite and granular-type retained austenite particles, but reduces fraction of bainite. The increase in retained austenite volume fraction is attributed to strain-assisted diffusion of carbon and to refinement of retained austenite particles.

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Herein, the occurrence of a B2‐phase separation and formation of Cr‐rich nano‐precipitates during the solidification process of AlCoCrFeNi2.1 eutectic high‐entropy alloy is addressed. Toward this end, various advanced characterizations, including high‐resolution transmission electron microscopy and atom probe tomography combined with thermodynamic calculations, are employed. The as‐solidified microstructure is composed of face‐centered cubic (FCC) dendrites and interdendritic regions consisting of a eutectic mixture of FCC and body‐centered cubic (BCC) phases. The presence of uniformly distributed Cr‐rich nano‐precipitates is traced through the BCC B2 phase in the interdendritic area. Regarding the occurrence of upward diffusion and Gibbs free energy variation, the formation of Cr‐rich nano‐precipitates is attributed to the spinodal decomposition where the critical temperature of 800 °C is passed behind during the solidification process. The formation of dense dislocation array in the interdendritic region due to thermal stress induced during solidification is introduced as a pathway for diffusion of alloying elements in the course of cooling stage.

In this research, a method is presented for predicting macroscopic plastic flow behavior of a quench and partitioning (Q&P) steel using data of nanoindentation experiments.The method is based on Tabor’s model in which nanohardness values obtained with indenters of different angles to be connected to the flow behavior of the indented material. The process consists of two steps: (i) the macroscopic flow relation of each microphases assessed based on the characteristic strain and constraint factor, (ii) the total flow curve of the steel extracted through an isostrain manner. A rationally successful prediction of the macroscopic plastic flow of the Q&P steel is obtained from the constituent phases properties due to consideration of the indentation size effect and application of a rule of-mixture. Eventually, the accuracy of the estimation is verified by comparing the predicted stress-strain curve to the tensile curve obtained from a standard bulk sample.

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