Newly developed Mg-8Al-1Zn-0.6Ca-0.3La-0.3Mn alloy having outstanding extrudability and good strength-ductility synergy

Improving the extrusion speed of magnesium alloys is crucial for expanding their applications. In this work, we report a novel heavily-alloyed Mg-8.0Al-1.0Zn-0.6Ca-0.3La-0.3Mn (AZXLM81100, wt.%) alloy that exhibits outstanding extrudability and good mechanical performance. The alloy can be extruded at a die-exit speed of 32.4 m/min. The excellent high-speed extrudability is attributable to its relatively high incipient melting temperature (604.2 °C), which results from the formation of thermally stable Al2Ca and Al8Mn4La phases. In addition to micron-sized Al2Ca and Al8Mn4La fragments, a limited number of nanoscale (Mg,Zn)17Al12 and Mn particles are also uniformly dispersed in the high-speed-extruded AZXLM81100 alloy. Moreover, the as-extruded AZXLM81100 rod displays a fully dynamically recrystallized microstructure, characterized by a typical basal texture and fine grains with an average grain size of 6.5 ± 0.7 μm. Owing to significant grain boundary strengthening and precipitation hardening, the as-extruded alloy achieves a high tensile yield strength of 250.8 ± 3.5 MPa. Furthermore, the coordinated activation of basal and non-basal dislocations, together with a small fraction of tension twins contributes to effective tensile deformation, resulting in a relatively high elongation of 15.2 ± 1.1 %. The newly developed AZXLM81100 alloy demonstrates considerable potential for the manufacturing of extruded profiles due to its excellent strength-ductility balance.