Abstract
The directional solidification of an Elektron 21 magnesium alloy is investigated by in situ synchrotron radiation tomography. To visualize the solidification process, samples of Elektron 21 are first heated to 800 °C, and the melt is held at this temperature for 5 min, to ensure temperature homogeneity. Subsequently, the samples are cooled with a cooling rate of 10 K min−1, while for every 35 s, one full tomogram is acquired. The evolution of the microstructure can be followed in 3D on the reconstructed tomograms. The contrast between rare‐earth metals and Mg enables to quantitatively analyze the changes in the morphology of the dendritic structure during solidification. At the onset of the detection, the growth of secondary dendrite arms occurs, which ends at the dendritic coherency point. From this temperature on, only the coarsening and coalescence of existing dendrite arms occurs.
Highlights
Mg-based materials are becoming increasingly attractive as structural materials due to their light weight, high specific strength, and good castability
The aim of this study is to investigate the phase formation during solidification in a commercial Elektron 21 alloy with in situ synchrotron radiation tomography and to quantify the morphological changes of the dendritic structure during the process
The initial microstructure of the Elektron 21 alloy was investigated by scanning electron microscopy (SEM)
Summary
Mg-based materials are becoming increasingly attractive as structural materials due to their light weight, high specific strength, and good castability. These properties enable them to substitute heavier counterparts in applications, where weight reduction and the consequent improvement in fuel efficiency is of importance.[1] biocompatible Mg alloys, when their corrosion rate is controlled, can be used in degradable implant applications, eliminating the need for a second, implant removal surgery.[2] During the development of Mg alloys for structural applications, one of the aims is to increase the generally poor creep resistance that impedes their use in fields where elevated temperature strength is required. Tolnai et al reported that the presence of Zn stabilizes the Mg3RE phase in Mg–Nd–Zn alloys[15] that was found to be the case in Elektron 21.[11]
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