Ductility enhancement in an as-extruded Mg-5.5Zn-0.8Zr alloy by Sm alloying

In this study, an as-extruded Mg-5.5Zn-0.8Zr-4Sm (ZK60-4Sm) alloy with enhanced ductility was fabricated and the microstructure and mechanical properties were investigated in detail. Results indicate that new micron (Mg, Zn)(3)Sm and nanoscale Mg41Sm5 phases are formed in ZK60-4Sm alloy and these undissolved eutectic phases distribute along the extrusion direction (ED). Other than that, a large number of nano-precipitated phases are observed in Mg matrix. In addition to being strengthening phases, the second phases can also pin dislocation and block grain boundary slip. According to Electron Back-Scattered Diffraction (EBSD) analysis, the addition of Sm has remarkable effect on promoting dynamic recrystallization (DRX) and grain refinement. Besides, the texture intensity of the alloys decreases significantly from 28.62 to 6.66. Owing to the joint effect of grain refinement, second phase strengthening and texture weakening, the yield strength (YS) and elongation (EL) of ZK60-4Sm alloy are improved significantly. In particular, the elongation (EL) of ZK60-4Sm alloy is increased by 100% compared with that of ZK60 alloy (14.1%), reaching 28.1%. Thus, a new as-extruded ZK60-4Sm alloy with enhanced ductility is obtained. (C) 2019 Elsevier B.V. All rights reserved.