Analysis on micro-structure and mechanical properties of Mg-Gd-Y-Nd-Zr alloy and its reinforcement mechanism

Abstract

Gd in Mg-RE liquid alloy has a high solid solubility, which can rapidly decreases with the drop of temperature. Thus the solid solution and aging reinforcement of liquid Mg alloy can be achieved. The micro-structure and mechanical properties of Mg-Gd-Y-Nd-Zr alloy under as-cast and aging state were studies by composition analysis, micro-structure observation and mechanical properties test, and the reinforcement mechanism of mechanical properties was analyzed. Results show that the micro-structure of as-cast alloy is mainly composed of α-Mg matrix and eutectic phase. The dendritic eutectic phase exhibits a discontinuous mesh distribution along the grain boundary. And the average grain size of alloy is about 46μm. After aging treatment, the average grain size is 52μm and the eutectic phase can dissolve into α-Mg matrix completely. The massive particle phase distribute in grain boundary and their number increased significantly, which can strengthen the alloy effectively. The tensile strength and yield strength of alloy are improved significantly from as-cast to aging state. But the elongation shows a decreasing trend. The Gd after dissolved into α-Mg matrix can lead to serious lattice distortion, improve the antiphase domain boundary and further improve the alloy yield strength.