Effect of Grain Size on Formability and Deformation Mechanism of High‐Purity Aluminum during Micro‐Embossing Process at Elevated Temperature

Due to the high processing efficiency, the low manufacturing cost, and the emission of carbon dioxide, microforming attracts considerable attention in the field of microelectromechanical systems. Thus, the micro‐embossing process is carried out for the high purity Al of coarse‐grained (CG) and ultrafine‐grained (UFG) microstructure at temperature ranging from 373 to 523 K. The interactive effects of grain size and temperature on formability are investigated. The results indicate that UFG pure Al is of better geometrical accuracy and surface quality in comparison with CG pure Al. Meanwhile, with the increasing temperature, the filling behavior of UFG pure Al is optimized and both CG and UFG pure Al reach full filling after embossing process at 523 K. Based on the observation of the microstructure of embossed ribs, plastic deformation together with the heat effect trigger the recrystallization of the CG pure Al and the grain growth of the UFG pure Al. The deformation mechanisms of CG and UFG pure Al are clarified, according to the evolution of misorientation angle distribution and kernel average misorientation. It is confirmed that intergranule movement for UFG pure Al includes grain boundary sliding and grain rotation accounted for the excellent formability.