Modification of long period stacking ordered phase and improvement of mechanical properties of Mg-Gd-Zn-Zr alloy by friction stir processing

The effect of friction stir processing (FSP) on the modification of microstructure and mechanical properties of Mg-14Gd-23Zn-0.6Zr (wt%) alloy has been investigated. The coarse long period stacking ordered (LPSO) phase at grain boundary in the alloy was successfully broken into fine particles (similar to 1 mu m) due to the complicated deformation beneath the shoulder and around the pin. The grain size was also significantly refined from 23 +/- 4 mu m to 1.6 +/- 0.3 mu m through dynamic recrystallization (DRX) during FSP. Yield strength of the FSP sample was increased by similar to 30% probably due to the grain size and LPSO phase refinement as well as fine precipitation around the LPSO phase while the elongation decreased by similar to 39% maybe because of the heterogeneous microstructure. (C) 2013 Elsevier B.V. All rights reserved.