Characterisation of β Phase in WE54 Magnesium Alloy

Abstract

Precipitation hardened magnesium-rare earth alloys offer attractive properties for the aerospace and racing automotive industries. The most successful magnesium alloys developed to date have been those based on the Mg-Y-Nd system identified as WE54 (Mg-5.0wt%Y-4.1wt%RE-0.5wt%Zr) and WE43 (Mg-4.0wt%Y-3.3wt%RE-0.5wt%Zr), where RE represents neodymium-rich rare earth elements. Precipitations sequence in WE-system alloys involved the formation of phases designated β”, β’, β1 and β depending on the ageing temperature. WE54 alloy with the equilibrium β-phase exhibits good ductility and medium tensile strength. The β phase precipitated in Mg-Y-Nd alloy during ageing at 300 °C was studied using X-ray diffraction analysis and transmission electron microscopy. Precipitation at 300 °C for one hour causes formation of the equilibrium β phase. This phase has an f.c.c. structure (a = 2.2 nm), which makes it isomorphous with Mg5Gd. With the prolonged ageing time at 300 °C, the volume fraction of the β phase increases and lattice parameter of the solid solution of α-magnesium decreases.

The Electrochemical and Immersion Corrosion of Casting Magnesium Alloys Containing Rare Earth Elements

“…Magnesium alloys of the Mg-RE-Zr group in as-cast condition are characterized by a structure of α-Mg solid solution with precipitates of intermetallic phases along grain boundaries and within the solid solution grains. Mg 41 Nd 5 and Mg 24 Y 5 [6] phases are observed in the WE43 alloy, Mg 2 Y, Mg 24 Y 5 i Mg 12 YNd [7] in the WE54 alloy and Mg 3 (Nd,Gd) type phase has been found in the EV31A alloy. The volume fraction of the intermetallic phases is similar in all alloys and is equal about 6% [9].…”

Microstructure evolution and mechanical properties of Mg–Nd–Y alloy in different friction stir processing conditions

“…The coarse eutectic structures located at the grain boundaries (shown by arrows B) are Nd-rich phases as shown in Table 2. It is reported that the coarse phases distributed along the grain boundaries in cast Mg-Nd-Y alloy are considered as Mg 41 Nd 5 [34,35] or Mg 12 Nd [9,27,36]. Since the atomic ratio of Mg and Nd is higher than 12, the coarse phase B is possibly Mg 12 Nd phase with oversaturated Mg atoms.…”

“…4(d) shows the high magnification image of rectangular particle, and EDS analysis shows that it is Y-rich phase. The rectangular shaped particle was represented as Mg 24 Y 5 in a lot of investigations [27,34,36]. According to the chemical composition and morphology, the rectangular particles exhibit in BM and FSP samples are Mg 24 Y 5 .…”

Structure, mechanical and corrosion properties of extruded Mg-Nd-Zn, Mg-Y-Zn and Mg-Y-Nd alloys

“…On the other hand, inferior heat stability limited the field of use of magnesium. Nowadays, some magnesium alloys may withstand the temperatures up to 300°C without significant loss of mechanical properties [2]. Recently, magnesium was discussed also as a material for biodegradable implants due to its biocompatibility and degradation performance.…”