Enhancing the strength-ductility balance in Mg–Zn alloys via regulating bimodal grain structures by α-Mn nanoparticles

Mg and its alloys have been widely applied in the automotive, aerospace, and electronic 3C industries. However, achieving a good strength-ductility synergy remains a challenge, especially for Mg alloys without rare earth elements. Here, we have developed an effective approach to regulate the grain size ratio and quantity of the unrecrystallized grain region in the bimodal grain structures during dynamic recrystallization by adding Mn (1.0–3.0 wt.%) to Mg–4Zn alloys. This has led to a concurrent enhancement in tensile yield strength (TYS) from 153 MPa to 208 MPa and elongation (EL) after fracture from 22 % to 27 %. The excellent strength and ductility of the Mg–Zn–Mn alloys are closely related to the combined effects of refined dynamically recrystallized grains, appropriate unrecrystallized grains, α-Mn nanoparticles and MgZn 2 precipitates. This strategy not merely facilitates a profound comprehension of the intricate relationship between the microstructure and mechanical properties of Mg alloys, but also contributes to the successful utilization of the bimodal grain structural design to achieve a concerted enhancement in both the strength and ductility of Mg alloys.