Abstract
? 2022 Elsevier B.V.Ultrasonic vibration (UV) is capable of improving material flowability and surface quality of products, thus the UV-assisted micro-forming process has become a fascinating technology for fabricating micro-parts. However, when the part is downscaled to the submillimeter level, the rheological behavior of the material during UV-assisted plastic deformation will be significantly affected by the ultrasonic and size effects, which are still not well understood. Meanwhile, the rheological behavior and microstructure evolution of advanced multi-component alloys under UV-assisted deformation are unclear. In this research, a set of UV-assisted micro-compression tests and characterization tests were carried out to investigate the role of grain size, geometrical dimension, and sound energy density on the rheological behavior and microstructure of CoCrFeMnNi high-entropy alloy (Cantor alloy). The results showed that Cantor alloy exhibits an unusual acoustic residual softening (ARS) phenomenon, which is related to the alleviation of severe lattice distortion effect and the increase of stacking fault energy during the UV. The value of ARS is not only related to the sound energy density but also affected by the grain size and geometrical dimension. Furthermore, mathematical models were developed to quantitatively characterize the ultrasonic softening (US) and ARS. The model evaluation showed that the proposed model can well predict the influence of grain size, geometrical dimension, and sound energy density on US and ARS. These findings provide a fundamental understanding for the UV-assisted micro-forming of Cantor alloy.
NSTL
Elsevier