Influence of extrusion ratio on dynamic recrystallization, microstructural evolution, and mechanical properties of Mg–5Bi–3Al alloy

This study investigates the influence of extrusion ratio (ER) on the microstructural evolution and tensile properties of a Mg–5Bi–3Al (BA53, wt%) alloy during hot extrusion. Extrusion was performed at ERs of 10, 25, 50, and 76, resulting in fully recrystallized microstructures across all extrudates. The BA53 alloy extruded at ER10 exhibited the finest grain structure, whereas relatively coarser grains were observed at ERs of 25–76; however, grain size remained comparable within this higher ER range. With increasing ER, the basal texture, characterized by the c -axis oriented perpendicular to the extrusion direction, became progressively stronger, although texture intensity was similar between ER50 and ER76. During extrusion, the residual Mg 3 Bi 2 phases present in the billet were increasingly fragmented with higher ER. In terms of mechanical performance, the tensile yield strength increased from 175 MPa at ER10 to 203 MPa at ER76, while elongation decreased from 13.8 to 7.9%. The enhancement in strength accompanied by reduced ductility was primarily attributed to texture strengthening induced by higher ER. Additionally, extrusion-butt analysis was performed to compare microstructures before and after die passage, as well as those of the final extrudates, thereby elucidating the influence of ER on dynamic recrystallization, texture evolution, and microstructural changes during static grain growth upon subsequent air cooling. These findings elucidate how extrusion ratio governs microstructural refinement, texture strengthening, and the resulting strength-ductility balance in the BA53 alloy.