MICROSTRUCTURE AND MECHANIAL PROPERTIES OF AS-EXTRUDED Mg-Sn-Al-Zn ALLOYS

摘要

Mg-(9-x)Sn-xAl-1Zn (x=1, 2, 3 and 4 wt.%) alloys weresubjected to indirect extrusion, and the microstructure andmechanical properties of these as-extruded Mg-Sn-Al-Zn (TAZ)alloys were investigated. The TAZ alloys contain only fineMg2Sn second-phase particles in the ?? -Mg matrix, and theamount of precipitates increase with increasing Sn contents. Inaddition, the TAZ 811 alloy shows finer grain structure than theTAZ 541 alloy due to a larger amount of Mg2Sn particles, whichact as nucleation sites for recrystallization and/or prevention ofgrain growth by the pinning effect. The textures of the alloysshow a typical basal pole orientation and an unusual <11-20>component in which one axis of the HCP unit cell is parallel to theextrusion axis. Tensile yield strength increases with Sn content,while ultimate tensile strength is almost identical due to theincreased strain hardenability with Al content. The tensioncompressionyield asymmetry decreases with reducing Sn content,which is mainly due to the decrease in the amount of particlespromoting twin nucleation.