Strong and ductile Mg-0.4Al alloy with minor Mn addition achieved by conventional extrusion

Abstract

Mg-0.4Al-xMn (x = 0, 0.3 and 1.5, in wt.%) have been produced by conventional one-step extrusion process. Mg-0.4Al-0.3Mn exhibits a simultaneously high tensile yield strength of 239 MPa and high fracture elongation (FE) of 30.1%. Besides, Mg-0.4Al-1.5Mn exhibits an extraordinary FE of 52.5% with a reasonable yield stress of 170 MPa. The Mn-containing alloys show a bimodal microstructure where the un-dynamically recrystallized (unDRXed) regions remain extruded fiber texture while the grains in the dynamically recrystallized (DRXed) regions exhibit fine grain size (~1 μm) and random orientation, instead of essentially DRXed grains in Mg-0.4Al with relatively coarse grain size (4.75 μm) and strong texture. Alloying Mn is expected to result in precipitates of α-Mn and Al8Mn5 in the alloys, which alters the behaviors of recrystallization nucleation and grain growth during extrusion and therefore the different microstructure formed in the Mg alloys with various Mn addition.