Effects of Gd, Y Content on the Microstructure and Mechanical Properties of Mg-Gd-Y-Nd-Zr Alloy

Changping Tang,Kai Wu,Quan Li,Wenhui Liu,Maomao Yang,Di Feng,Xiao Liu,Xuezhao Wang,Guodong Miao

doi:10.3390/met8100790

Abstract

The effects of Gd, Y content on the microstructure and mechanical properties of Mg-Gd-Y-Nd-Zr alloy were investigated using hardness measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and uniaxial tensile testing. The results indicate that the alloys in as-cast condition mainly consist of α-Mg matrix and non-equilibrium eutectic Mg5.05RE (RE = Gd, Y, Nd). After solution treatment, the non-equilibrium eutectics dissolved into the matrix but some block shaped RE-rich particles were left at the grain boundaries and within grains. These particles are especially Y-rich and deteriorate the mechanical properties of the alloys. Both the compositions of the eutectic and the block shaped particle were independent of the total Gd, Y content of the alloys, but the number of the particles increases as the total Gd, Y content increases. The ultimate tensile strength increases as the total Gd, Y content decreases. A Mg-5.56Gd-3.38Y-1.11Nd-0.48Zr alloy with the highest ultimate tensile strength of 280 MPa and an elongation of 1.3% was fabricated. The high strength is attributed to the age hardening behavior and the decrease in block shaped particles.

Highlights

Magnesium alloy is promising for applications in aircraft and automotive industries due to its low density, high specific strength, and high specific stiffness [1,2,3,4,5]
Samples with dimensions of 15 mm × 15 mm × 3 mm in as-cast and solution treated conditions for scanning electron microscopy (SEM) observation were prepared by mechanical grinding, polishing, and etching, and a solution of 4.0 vol% HNO3 with ethanol was prepared for etching, and the etching time was 20–30 s
SEM examination was performed in an FEI Quanta-200 (FEI, Eindhoven, The Netherlands) scanning electron microscope, and the chemical composition of the second phase in the alloy was analyzed using an equipped energy dispersive spectrometer (EDS)

Summary

Introduction

Magnesium alloy is promising for applications in aircraft and automotive industries due to its low density, high specific strength, and high specific stiffness [1,2,3,4,5]. Studies [6,7,8,9,10,11] indicated that addition of rare earth elements is an effective method to improve the mechanical properties of magnesium alloy, such as Gd, Y, Nd etc. The element Gd has a high solubility in magnesium, which is about 24% at 542 ◦ C, and the solubility decreases with decreasing temperature [12]. This feature creates conditions for aging, and the excellent precipitation strengthening effect results in the Mg-Gd series becoming one of the alloys with the highest strength. Wang et al [8] first reported a high-strength

Methods

Results

Conclusion