Effects of Si addition on microstructure and mechanical properties of Mg-8Gd-4Y-Nd-Zr alloy

Effects of Si addition (1.0 wt.%) on microstructure and mechanical properties of Mg-8Gd-4Y-Nd-Zr alloy have been investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrum (EDS), X-ray diffraction (XRD), hardness measurements and tensile testing. The results indicated that the addition of Si led to the formation of Mg2Si and (RE + Si)-rich particles, which enhanced the Young's modulus of the alloy by 7 GPa while decreased the yield strength and ultimate strength by 10 MPa and 31 MPa, respectively. The tensile properties of the Mg-8Gd-4Y-Nd-Zr-Si alloy are as follows: Young's modulus E = 51 GPa, yield strength sigma(0.2) = 347 MPa, ultimate strength sigma(b) = 392 MPa and elongation delta = 2.7%. The increase in Young's modulus was attributed to the formation of particles with high Young's modulus, while the decrease in strength was ascribed to the decrease in volume fraction of metastable beta' precipitates caused by the consumption of rare earth atoms due to the formation of the rare earth containing particles. (C) 2012 Elsevier Ltd. All rights reserved.