**Edwin Eyram Klu 1, Dan Song 1,2,3,\*, Chen Li 1, Guowei Wang 1, Zhikai Zhou 1, Bo Gao 4, Jiapeng Sun 1, Aibin Ma 1,2 and Jinghua Jiang 1,\***


Received: 29 August 2019; Accepted: 11 September 2019; Published: 14 September 2019

**Abstract:** In this study, a high-strength Mg-9Li alloy was developed via multi-pass equal-channelangular-pressing (ECAP) and post rolling, of which the yield tensile stress (YTS) and ultimate tensile stress (UTS) were 166 MPa and 174 MPa representing about 219% and 70% increase in YTS and UTS respectively, compared to the cast alloy. The cast alloy was ECAP processed at 200 ◦C for 4, 8, and 16 passes, followed by room-temperature rolling to a total thickness reduction of 50%. The 8-passes ECAPed (E8) alloy presented the best strength of all the ECAPed alloys, and the post rolling endowed the alloy (E8R) further strengthening and the best strength of all the alloys. Grain-boundary strengthening and dislocation strengthening were the two major factors for the high strength of the processed alloys. The α-Mg phase grains were greatly refined to about 2 μm after 8-passes ECAP, and was further refined to about 800 nm ~1.5 μm after rolling. Significant grain refinement endowed the alloy with sufficient grain-boundary strengthening. Profuse intragranular dislocation accumulated in the deformed matrix, leading to the significant dislocation hardening of the alloy. Rolling-induced strong basal texture of the α-Mg phase also enhanced the further strengthening of the E8R alloy.

**Keywords:** Mg-9Li duplex alloy; ECAP; rolling; high strength; microstructure
