Asymmetric Extrusion Technology of Mg Alloy: A Review

Abstract

Magnesium (Mg) alloy is a widely used lightweight metal structural material due to its high specific strength and stiffness, excellent damping performance, and recyclability. Wrought Mg alloys are particularly favored in fields such as aerospace, transportation, and biomedical stents. However, most wrought Mg alloys with a hexagonal close-packed (HCP) crystal structure lack sufficient independent slip systems to meet the von Mises criterion for uniform plastic deformation at room temperature. This can result in the formation of a strong basal texture during plastic deformation and poor room temperature plastic formability. Enhancing the room temperature forming performance is therefore a crucial challenge that needs to be addressed in order to expand the application of Mg alloy sheets. Our research group has comprehensively summarized significant work and the latest research progress in improving the room temperature forming of Mg alloy sheets via extrusion technology in recent years. Specifically, we have developed a new type of asymmetric extrusion technology that combines material structure evolution, mechanical properties, and forming behavior analysis. We have elucidated the extrusion process characteristics, texture control mechanism, and forming properties of Mg alloy sheets through plastic deformation mechanisms, mold design, and finite element numerical simulation. The findings of our study present an innovative extrusion technology for the fabrication of highly formable Mg alloy sheets, which can be utilized in various applications.

Structural Phenomena Introduced by Rotary Swaging: A Review

“…Keeping in mind the Hall-Petch law, especially the ultra-fine grained (UFG) and nano-materials have been intensively researched (e.g., [24,25]). To achieve the final grain size in such small scales, numerous methods of severe plastic deformation (SPD)-for example, Equal Channel Angular Pressing (ECAP) [26][27][28][29][30]-various ECAP modifications [31][32][33][34][35][36][37][38][39]-High Pressure Torsion (HPT) [40,41], Friction Stir Processing (FSP) [42], or Accumulative Roll Bonding (ARB) [43,44]-and intensive plastic deformation, i.e., IPD, methods (e.g., asymmetric reduction rolling [45,46], (high speed ratio) differential speed rolling [47], and asymmetric extrusion [48], etc., have been introduced. In principle, the methods are based on imposing high, or extreme, shear strain into the processed (metallic) materials, the effect of which being that they impart (substantial) grain refinement via introducing lattice distortions and crystallographic defects leading to the development and accumulation of dislocations according to the above-described schemes (depending on the intrinsic properties of the metallic material).…”