Achieving high compressive strength-ductility in bcc based Mg–Li-Sc alloys with bimodal hcp duplex microstructure

A bimodal microstructure consisting of blocky and lamellar α-hcp phases within a β-bcc matrix was first created in Mg–Li-Sc alloys by solution treatment at 540–580 °C, followed by water quenching. This distinctive structure effectively addresses the typical strength-ductility trade-off in Mg–Li-based alloys. Sc improves mechanical performance mainly through two mechanisms: solid-solution strengthening, which contributes about 40% to the compressive yield strength, and phase refinement, responsible for roughly 30%. The lamellar α-hcp acts as an efficient phase refiner and has Li and Sc contents similar to those of the β-bcc phase, working together to enhance strength. The Mg–15Li–5Sc (at. %) alloy, when solution-treated at 580 °C, exhibits an impressive combination of properties: a yield strength of 273.6 MPa, an ultimate compressive strength of 611.2 MPa, and ductility of 28.7%. Similarly, the Mg–13Li–7Sc (at. %) alloy, under identical treatment, exhibits an even higher yield strength of 299.0 MPa while maintaining good ductility of 22.2%.