High-temperature mechanical behavior of extruded Mg-Y-Zn alloy containing LPSO phases

Abstract

The high-temperature mechanical behavior of extruded Mg97-3x Y2x Zn x (at. pct) alloys is evaluated from 473 K to 673 K (200 C to 400 C). The microstructure of the extruded alloys is characterized by Long Period Stacking Ordered structure (LPSO) elongated particles within the magnesium matrix. At low temperature and high strain rates, their creep behavior shows a high stress exponent (n = 11) and high activation energy. Alloys behave as a metal matrix composite where the magnesium matrix transfers part of its load to the LPSO phase. At high-temperature and/or low stresses, creep is controlled by nonbasal dislocation slip. At intermediate and high strain rates at 673 K (400 C) and at intermediate strain rates between 623 K and 673 K (350 C and 400 C), the extruded alloys show superplastic deformation with elongations to failure higher than 200 pct. Cracking of coarse LPSO second-phase particles and their subsequent distribution in the magnesium matrix take place during superplastic deformation, preventing magnesium grain growth. © 2013 The Minerals, Metals & Materials Society and ASM International.