Microstructure and texture evolution in Mg-1 %Mn-Sr alloys during extrusion

摘要

Microstructure and texture evolution in Mg-1 %Mn-Sr alloys during extrusion has been investigated. At 350 C, the extrusion of Mg-1 %Mn (M1) alloy exhibits the progressive formation of basal texture from the undeformed zone to the die opening. The extruded microstructure of M1 consists of recrystallized grains nucleated by grain boundary bulging and elongated parent grains along with extensive twinning. At 350 C, the extrusion of M1-1.6Sr alloy results in progressive elongation of Mg-Sr precipitates in the form of stringers from the undeformed zone to the die opening. The final extruded microstructure of this alloy shows extensive recrystallization occurring at the intermetallic stringers by particle-stimulated nucleation (PSN). M1-(0.3-1.6)%Sr alloys display weaker textures due to PSN which creates new grains with random orientations. At 250 C, the extrusion of M1 creates necklace of small recrystallized grains around large elongated parent grains. M1-1.6Sr alloy extruded at 250 C exhibits continuous dynamic recrystallization (CDRX) in the Mg matrix and PSN at Mg-Sr precipitates. PSN is less extensive at lower temperature. Both CDRX and PSN grains have random orientations, and therefore, alloy develops random texture.