Karl Ulrich Kainer

Effects of Gadolinium and Neodymium Addition on Young’s Modulus of Magnesium-Based Binary Alloys

In order to investigate the influence of solute atoms and particles on Young’s modulus of magnesium, series of binary Mg–Gd and Mg–Nd alloys were prepared using hot extrusion. With increasing Gd content from 0 to 2.654 at.% Young’s modulus of Mg–Gd alloys increases linearly from 44.0 to 45.3 GPa. Regarding Mg–Nd alloys, Young’s modulus firstly decreases to 42.5 GPa until 0.184 at.% Nd, and then increases to 43.4 GPa at Mg–0.628 at.% Nd. The different influences of solutes Gd and Nd on Young’s modulus of Mg are attributed to their different solid solution behaviors in magnesium, which can lead to the alterations of crystal cell parameters and/or different amount of second phases. For Mg–Gd alloys the lattice parameters increase and the axial ratio (c/a) decreases with Gd content increasing. In contrast, for Mg–Nd alloys they almost keep unchanged due to small solubility of Nd in Mg when Nd content increases.

3D Microstructural Evolution on Solidifying Mg–5Nd–5Zn Alloy Observed via In Situ Synchrotron Tomography

In situ synchrotron tomography is a unique technique to study 3D microstructure evolution during solidification due to the high brilliance of the beam and the short acquisition time of the detector systems. In this work, in situ synchrotron tomographic observations were performed during the solidification of Mg–5Nd–5Zn (wt%) alloy with a cooling rate of 5 °C/min. The experiment was performed at the TOMCAT beamline of the Swiss Light Source (Paul Scherrer Institute (PSI), Villigen, Switzerland). The sample was melted using a laser-based heating system and then cooled until completely solidified. 3D tomograms were acquired during solidification. The microstructural analysis starts after the coherency point until the end of solidification. A differential thermal analysis (DTA) experiment was performed to estimate the liquidus and solidus temperature of the alloy. These values were used to correct the measured temperature from the in situ solidification experiment. Different microstructural parameters such as the volume fractions of the phases, i.e. α-Mg dendrites, interdendritics and pores, as well as the interconnectivity and skeletonization results are discussed.