DescriptionThe demand of light metals in the transportation sector is increasing owing to strict environmental regulations. Due to their specific strength Mg alloys with additions of Zn and Zr (ZKMg alloys) are a promising material for light weight applications. Furthermore, the introduction of rare earth (RE) elements can provide high temperature strength and creep resistance to this type of alloys. In this contribution, the 3D microstructure of a ZK60 (Mg – 6wt%Zn – 1wt%Zr) magnesium alloy with and without 1.5 wt% of RE is analyzed. The alloy is manufactured by permanent mold casting and thixo-casting using metallic magnesium, Zirmax hardener (Mg – 33.3wt%Zr), electrolytic zinc and mischmetall alloy. Cast blocks with a diameter of 118 mm and a length of 170 mm were produced. The 3D data was acquired using a commercially available X-ray computed tomography (XCT) system GE Phoenix|X-Ray Nanotom 180. The XCT results are complemented by light optical microscopy (LOM) and scanning electron microscopy (SEM). Three positions in z and x direction of the cast blocks were investigated to determine the homogeneity of the microstructure. Three consecutive scans were carried at each position to analyze local microstructural variations. A total of 27 high resolution scans with a voxel size of (1.6µm)3 were acquired for each alloy and casting route. Phases with higher density than the Mg matrix material appear as brighter grey areas in the CT scans. Intermetallics forming a 3D network with an interconnectivity >99% can be observed in the interdendritic region. The size of the dendritic cells decreases towards the bottom of the casting blocks. Furthermore, Zr-rich particles with a blocky structure (brightest particles in the XCT reconstruction) are found distributed inhomogeneously and tend to agglomerate at the bottom of the casting blocks.
|Period||19 Sep 2017|
|Event title||Euromat 2017, Thessaloniki: null|
|Location||Thessaloniki, Greece, Greece|