Papers by Keyword: Hot Deformation Simulation

Abstract: The demand to replace Fe-V steel with Fe-Nb steel is evolving because of high costs of raw vanadium material. For the mass production of Fe-Nb steel, the most critical barrier is a poor impact toughness comparing with that of Fe-V steel. This study covers a microstructural investigation for ferrite grain size to explain the strength and toughness results as a function of V and Nb contents. The steel samples were made of three different compositions, i.e., Fe-V steel (Fe-0.05V-0.001Nb), Fe-V-Nb steel (Fe-0.014V-0.03Nb), and Fe-Nb steel (Fe-0.003V-0.033Nb). Rolling temperature to initiate was 1150°C for the all experiments. However, rolling temperature to finish was set differently for two conditions; 950°C and 860°C. The rolling to 860°C decreased the grain size for the ferrite phase and increased the impact toughness rather than the case of 950°C. The Fe-V-Nb steel exhibited similar value of the impact toughness with that for the Fe-V steel because of the low rolling temperature to finish, i.e., 860°C. The whole replace of V with Nb decreased the impact toughness significantly, however some extent of V content remained with Nb content showed the comparable toughness to the Fe-V steel by optimizing the controlled rolling process.

Abstract: The hot compression deformation behavior of AZ61B magnesium alloy has been investigated by using a Gleeble-1500D thermal simulator. The samples were compressed to a reduction of 50% at two temperatures (623 and 673K) with different strain rates (0.01, 0.1 and 1s-1). The relationships between flow stress and deformation temperature were analyzed, and the deformation activation energy and stress exponent were calculated based on the experimental results. With aid of the optical microscopy, scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD) techniques, the microstructure and micro-texture of the deformed samples were characterized. The effects of the temperature and strain rates on the hot compression behavior of the AZ61B magnesium alloy have been investigated by detail analyses of the flow stress and microstructural characteristics of the deformed samples. For the 50% compressed samples, dynamic recrystallization occurred during the hot compression. The orientations of the dynamic recrystallized grains with equiaxed shape were investigated by EBSD technique. The relationships among the flow stress, dynamic recovery and recrystallization have been discussed by considering both the temperature and strain rate effects.