Single-pass hot compression tests are performed to study the hot deformation behavior of a low carbon microalloyed steel at temperatures in the range of 950-1050 C and strain rate from 0.01 to 0.5 s-1. Based on true stressstrain data, the effect of strain rate and temperature on the flow behavior of this steel is analyzed and peak stress is determined as well. The partial derivative of the strain hardening rate to stress is used to determine the critical stress. The value of activation energy and the ratio of critical stress (strain) to peak stress (strain) are estimated. The relationship between characteristic points and Zener-Hollomon parameter is established. The kinetic model for the calculation of volume fraction of dynamic recrystallization is also established. The strain dependence of material constants are determined from fifth-order polynomials and the flow stresses under different deformation conditions are predicted, consistent with the experimental results. Figure 7. Comparisons between measured and predicted flow stress at different strains. www.advancedsciencenews.com www.steel-research.de steel research int. 2018, 89, 1700395

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The essence of the rough set theory (RST) is to deal with the inconsistent problems by two definable subsets which are called the lower and upper approximations respectively. Asymmetric Similarity relation based Rough Sets (ASRS) model is one kind of extensions of the classical rough set model in incomplete information systems. In this paper, we propose a new matrix view of ASRS model and give the matrix representation of the lower and upper approximations of a concept under ASRS model. According to this matrix view, a new method is obtained for calculation of the lower and upper approximations under ASRS model. An example is given to illustrate processes of calculating the approximations of a concept based on the matrix point of view.

Based on solid solution theory, mass conservation law and classical nucleation, growth and coarsening theory, a thermo/kinetic model is developed to predict the precipitation behavior of complex precipitates in Nb‐V bearing steel. The equilibrium composition of matrix and precipitates is calculated by the thermodynamic model and is input in the kinetic model to calculate the driving force for precipitation at a given temperature. The diffusivity and concentration of alloying elements is considered in the entire precipitation process. The effect of interfacial energy of precipitates and activation energy on precipitation behavior are studied. Simulation results indicate that the interfacial energy plays a significant role in the entire process of precipitation and there is no overlap between nucleation and coarsening when the interfacial energy is in the range of 0.5–0.55 Jm−2. The mean particle diameter predicted by the proposed model is compared with the experimental results and a good agreement was obtained.