Effects of homogenization temperature on microstructure and mechanical properties of high-speed-extruded Mg–5Bi–3Al alloy

摘要

This study investigates the effects of billet homogenization temperature on the dynamic recrystallization behavior during high-speed extrusion and resultant microstructure and tensile properties of the Mg–5Bi–3Al(BA53,wt%)alloy.Two billets homogenized at 350 and450℃(350H and 450H billets)are extruded at a high speed of 69 m/min.The 350H billet has a relatively smaller grain size and a higher abundance of fine Mg3Bi2particles compared to the 450H billet.During extrusion of the 350H billet,enhanced dynamic recrystallization occurs as a result of its finer grains and abundance of particles,while the growth of recrystallized grains is suppressed by the grain-boundary pinning effect of particles.Ultimately,the extruded 350H material is characterized by smaller grains,relatively greater number of Mg3Bi2particles,and a higher internal strain energy than the extruded 450H material.The tensile strength of the extruded 350H material is higher than that of the extruded 450H material owing to stronger grain-boundary hardening,particle hardening,and strain hardening effects.The extruded 350H material also exhibits a higher tensile elongation as its smaller grains inhibit the formation of crack-inducing undesirable twins during tension.The results from this study demonstrate that a decrease in the homogenization temperature from 450 to 350℃leads to improved strength and ductility in the high-speed-extruded BA53 material.