The microstructure and texture evolution of Mg-5Sn-1Si-0.8Y alloy during the reciprocating extrusion process (REP)

In this paper, the microstructure and texture evolution of Mg-5Sn-1Si-0.8Y alloy fabricated by reciprocating extrusion process (REP) at 340 ℃ for 2–8 passes is characterized by optical microscopy (OM), Scanning Electron Microscope (SEM) and Electron Backscatter Diffraction (EBSD). The results show that the microstructure was refined significantly, dynamic recrystallization (DRX), fragmentation of the second Mg2Si phase and precipitation of the Mg2Sn phase occurred during REP. With the increase of the REP passes, the fraction of low angle grain boundaries (LAGBs) showed a decreasing trend and the secondary phases distribution became more and more homogeneous and the degree of DRX was increased. At the same time, the initial extruded fiber basal texture was gradually weakened and became random as the REP passes increases. The hardness of the alloy also shown an increasing trend with the increase of REP passes. The grain refinement mechanism, texture evolution and increase of hardness were mainly related to the dynamic recrystallization and the particle stimulation nucleation (PSN) effect of the second phases.