Tensile properties of hot rolled Mg-3Sn-1Ca alloy sheets at elevated temperatures

Mechanical behavior of hot rolled Mg-3Sn-1Ca (TX31) magnesium alloy sheets were studied in the temperature range 25-350 degrees C. The microstructure of the alloy consisted of the eutectic structure of alpha-Mg + Mg2Sn and a dispersion of needle-like CaMgSn. The highest room-temperature ductility of 18% was obtained by hot rolling of the cast slabs at 440 degrees C, followed by annealing at 420 degrees C. The high temperature tensile deformation of the material was characterized by a decrease in work hardening exponent (n) and an increase in strain rate sensitivity index (m). These variations resulted in respective drops of proof stress and tensile strength from 126.5 MPa and 220 MPa at room temperature to 23.5 MPa and 29 MPa at 350 degrees C. This was in contrast to the ductility of the alloy which increased from 18% at room temperature to 56% at 350 degrees C. The observed variations in strength and ductility were ascribed to the activity of non-basal slip systems and dynamic recovery at high temperatures. The TX31 alloy showed lower strength than AZ31 magnesium alloy at low temperatures, while it exhibited superior strength at temperatures higher than 200 degrees C, mainly due to the presence of thermally stable CaMgSn particles. (C) 2011 Elsevier Ltd. All rights reserved.