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Sealing problems, subsequent cleaning processes and poor force transmission effect etc. series of problems which strongly restrict the development and application of traditional medium pressure-based sheet forming technology. To overcome these problems, the magnetorheological fluid (MRF) can be used as the alternative force transmission medium. In this study, the deep drawing process of a 304 stainless steel sheet using MRF was investigated. The die cavity was filled with MRF and electric current was used to quantitatively adjust the magnetic fields distribution, which then controls the deformation behavior of the forming sheet. As compared to the conventional deep drawing process, experimental results clearly show that significant improvement in the produced sample quality was obtained when using the MRF with the electric current of 2 A. These improvements include: the height of the boundary circle reduces by 20%, the wall thickness distribution is more uniform, the rebound ratio correspondingly reduces from 9.6% to 0.67%, and the degree of sticking mode and the size precision are significantly increased. The results of this study provide scientific guidance to solve the bottleneck in the traditional deep drawing forming technology. The potential applications of the MRF-based new deep drawing technology to improve the product quality were explored. [ABSTRACT FROM AUTHOR]

The process condition is one of the major factors to the quality of the matched cold-pressing joining between dissimilar sheets. The material AA1100 pure aluminum sheets and 304 stainless steel sheets were taken for experimental studying in this article. It was reached systematically that the effects of process conditions such as the loading pressure, the thickness of the aluminum sheets, and the joint structure on joining process and quality. As results shown, there was shunt behavior on the joint area of the aluminum sheet. The thickness of the joining decreased from the center to the both sides sequentially. The thickness of the aluminum sheets was proportional to the joining strength, and the loading pressure was inversely proportional to the joining strength when the other parameters were all the same. The technical reserves for the development of cold-pressing joining deformation joining for dissimilar sheets were provided in this study. [ABSTRACT FROM AUTHOR]

The hot deformation behaviors of an ultrafine-grained MoNbTaTiV refractory high entropy alloy (RHEA) fabricated by powder metallurgy (P/M) were investigated using isothermal compression tests in the deformation temperature range of 1100 °C ~ 1300 °C and the strain rate range of 0.0005 s−1–0.5 s−1. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) techniques were used to analyze the effect of the deformation temperatures and the strain rates on the flow stress behaviors and microstructural evolution during hot deformation. The results showed that the flow stresses exhibit typical dynamic recrystallization (DRX) characteristics, but show work hardening characteristics at 1100 °C and 0.5 s−1 deformation conditions and at 1200 °C and 0.5 s−1 deformation conditions. With increasing deformation temperature and decreasing strain rate, the maximum compressive stresses were dramatically decreased, and the average grain sizes also slowly increased. The limited growth of grains was due to the sluggish diffusion effect of high entropy alloys (HEAs) and the pinning effect of the ultrafine precipitated phases. The dominant DRX process gradually changed from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX) with increasing deformation temperature and decreasing strain rate. Both of these DRX processes were promoted by the ultrafine precipitated phases. The dominant deformation mechanism at low deformation temperature and high strain rate was grain deformation. Grain boundary gliding became the dominant deformation mechanism at higher deformation temperature and lower strain rate, but it was inhibited to some extent by grain growth and the ultrafine precipitated phases distributed at grain boundaries. [ABSTRACT FROM AUTHOR]