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a b s t r a c tUsing a Thermecmastor-Z hot simulator, dynamic recrystallization (DRX) and static recrystallization (SRX) behavior of a Nb-microalloyed steel was investigated by single-hit compression tests and double-hit compression tests, respectively. The experimental results show that DRX will more easily occur at higher deformation temperature and lower strain rate. The deformation activation energy and stress exponent for the Nb-microalloyed steel are calculated to be 379.29 ± 23.56 kJ/mol and 5.76 in temperature range of 950°C to 1100°C by regression analysis, respectively. Furthermore, a semi-empirical model is developed to identify the peak stress and strain for DRX. It is found that SRX kinetics follows Avrami's law, and the softening fraction predicted by the model agrees well with experimental results.

In this paper, the behavior of a micron-scale fluid droplet on a heterogeneous surface is investigated using a two-phase lattice Boltzmann method (LBM). The two-phase LBM permits the simulation of the time dependent three-dimensional motion of a liquid droplet on solid surface patterned with hydrophobic and hydrophilic strips. A nearest-neighbor molecular interaction force is used to model the adhesive forces between the fluid and solid walls. The solid heterogeneous wall is a uniform hydrophilic substrate painted with hydrophobic strips. The model is validated by demonstrating the consistency of the simulation results with an exact solution for capillary rise and through qualitative comparison of computed dynamic contact line behavior with experimentally measured surface properties and observed surface shapes of a droplet on a heterogeneous surface. The dependence of spreading behavior on wettability, the width of hydrophobic strip, initial location of the droplet relative to the strips, and gravity is investigated. A decrease in contact angle of the liquid on a hydrophilic surface may lead to breakup of the droplet for certain substrate patterns. The simulations suggest that the present lattice Boltzmann (LB) model can be used as a reliable way to study fluidic control on heterogeneous surfaces and other wetting related subjects.

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Mécanique des fluides numérique / convection thermique-vibratoire / lattice-Boltzmann / interfaceAbstract : The response of a two-phase stratified liquid system subject to a vibration parallel to an imposed temperature gradient is analyzed using a hybrid thermal lattice Boltzmann method (HTLB). The vibrations considered correspond to sinusoidal translations of a rigid cavity at a fixed frequency. The layers are thermally and mechanically coupled. Interaction between gravity-induced and vibration-induced thermal convection is studied. The ability of applied vibration to enhance the flow, heat transfer and interface distortion is investigated. For the range of conditions investigated, the results reveal that the effect of vibrational Rayleigh number and vibrational frequency on a two-phase stratified fluid system is much different than that for a single-phase fluid system. Comparisons of the response of a two-phase stratified fluid system with a singlephase fluid system are discussed. Computational fluid dynamics/ thermal vibrational convection / lattice-Boltzmann / interface

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