Proceedings of the 8th Pacific Rim International Congress on Advanced Materials and Processing pp 1123-1130 | Cite as
Microstructural Characterization of Metastable Phases in Homogenised and Aged Mg-Nd and Mg-Gd-Nd Alloys Containing Zn, Y and Zr
Abstract
Microstructure and phase evolution in Mg-Gd and Mg-Gd-Nd based alloys with additions of Zn, Zr and Y were analyzed in the as-cast, solution treated and aged conditions. Alloys has been investigated after solution treatment at 540°C for 24hr followed by isothermal aging at 175°C up to 125 days by using of Vickers hardness, optical microscopy, scanning electron microscopy equipped with EDS, X-ray diffraction and transmission electron microscopy. It was found that the as-cast alloys contained primary a-Mg matrix, eutectic-like structures, cuboid-like phases and Zr-rich clusters. The homogenized and quenched alloys contained primary a-Mg solid solution, smaller amount of divorced eutectic compounds, enlarged cuboid-like particles and Zr-rich clusters. The eutectic phase was Mg5Gd prototype with the composition Mg5(GdxNd1−x, x≈0.2). The cuboid shaped phases have a FCC structure with a≈0.54nm. The compositions of the cuboid shaped particles were found as Gd0.7(Y x Mg1-x)0.3 with x≈0.5 in the Mg-5Gd based alloy, and Gd4(YxNd1-x) with x≈0.5 in the Mg-6Gd-3.7Nd based alloy. The cuboid shaped particles appeared to be stable during subsequent aging at 175°C. Precipitation of β″’, β′ and β1 phases during aging was observed.
Keywords
Mg-Gd alloys Mg-Gd-Nd alloys Precipitation Microstructure Mechanical propertiesPreview
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