Grain Refinement of Pure Magnesium Using Nonlinear Twist Extrusion

Abstract

Nonlinear Twist Extrusion (NTE) is a new severe plastic developed (SPD) method for producing grain refinement by extruding and twisting bulk materials through the channel designed for more effective straining compared with the so-called twist extrusion (TE). In this experiment pure magnesium was pressed using NTE for up to 4 passes. The pressing was conducted under two different temperatures, the first pass was conducted in 523K followed by pressing from 2 to 4 passes at 473K pressing temperature. The microstructure of the material is observed with increasing number of passes using optical microscopy (OM), laser microscope and scanning electron microscopy (SEM) electron backscattered diffraction (EBSD). Grain size decreased with increasing passes and become finer than those obtained by other SPD processing. If compared by the same equivalent plastic strain, and it suggests that NTE is a promising approach in strengthening bulk material. The grain size of the as-received material reduced from 97μm down to 3μm after 4 passes. Moreover, the hardness of material also increasing up to 41Hv for the first pass and constantly increased with the increasing number of pressing. This result shows that NTE is one of the promising methods in severe plastic deformation.