BCC-Based Mg–Li Alloy with Nano-Precipitated MgZn₂ Phase Prepared by Multidirectional Cryogenic Rolling

Abstract

In this study, we deformed the single β phase Mg–Li alloy, Mg–16Li–4Zn–1Er (LZE1641), with conventional rolling (R) and multi-directional rolling (MDR), both at cryogenic temperature. Results showed that the nano-precipitation phase MgZn2 appeared in the alloy after MDR, but this phenomenon was not present in the alloy after R. The finite element simulation result showed that the different deformation modes changed the stress distribution inside the alloy, which affected the microstructures and the motion law of the solute atoms. The high-density and dispersively distributed MgZn2 particles with a size of about 35 nm were able to significantly inhibit the grain boundary migration. They further hindered the dislocation movement and consolidated the dislocation strengthening and fine-grain strengthening effects. Compared with the compressive strength after R (273 MPa), the alloy compressive strength was improved by 21% after MDR (331 MPa). After 100 °C compression, the MgZn2 remained stable.

Keywords

• bcc Mg–Li alloy
• cryogenic
• multi-directional rolling
• nano–grains
• dislocation
• MgZn₂ phase