Abstract
The thermal parameters of Mg-2.8Nd-1.5Gd-0.5Zn-0.5Zr cast alloy with 0.25 wt.% of erbium (Er) were evaluated by the computer-aided cooling curve thermal analysis(CA CCTA), whereas the microstructure analysis was investigated by the optical microscope and scanning electron microscopy. Results from the cooling curve and microstructure analysis showed that Er altered the grain size of the alloys. In addition, the grain size was reduced by approximately 19.6% with the addition of Er. Scanning electron microscopy results showed that Er formed an Mg-Zn-Nd-Er phase which distributed along the grain boundaries. Furthermore, the mechanical properties were investigated by hardness and tensile tests with Er addition. The addition of 0.25 wt.% of Er significantly improved the ultimate tensile strength and yield strength. In addition, the hardness value of Mg-2.8Nd-1.5Gd-0.5Zn-0.5Zr increased by 13.9% with Er addition.
Highlights
The request of weight reduction for structural materials has become increasingly strong in recent years[1]
Two groups of RE elements considered for Mg alloys are yttrium (Y), gadolinium (Gd), Erbium (Er) and dysprosium (Dy), which are highly soluble, and neodymium (Nd), cerium (Ce), and lanthanum (La), which are less soluble; both groups are used to improve the properties of Mg alloys [5]
The results showed that the Mg-Zn-RE phase of base alloy was formed at 526.8 °C and With addition of 0.25 wt.% Er, the TEuMg-Zn-RE temperature of Mg-Zn-RE phase decreased by 0.8 °C
Summary
The request of weight reduction for structural materials has become increasingly strong in recent years[1]. Magnesium light alloys have aroused increasing interest in recent years for applications in aerospace, aeronautics and automotive [2],due to their high strength weight ratio and low density excellent castability and good machinability [3, 4].Rare-earth (RE) metals are added to Mg alloys to improve their strength, microstructure and creep resistance. Adding Erbium into a Mg–Zn–Zr alloy improves the deformability of the latter and leads to the formation of a fine and uniform microstructure. Erbium can increase the thermal stability and improve the mechanical properties of the alloy structure [10]. This research aims to investigate the addition of Er separately on solidification ehaviour, microstructure and mechanical properties of Mg-Nd-Gd-Zn-Zr cast alloy
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