Three Dimensional Morphology of Mn Rich Intermetallics in AlSi Alloys Investigated with X-Ray Tomography

Abstract

Elementary Mn has a great importance as neutralizer of Fe intermetallics like β-Al5FeSi, which have detrimental effect on mechanical characteristics of AlSi alloys. Presence of Mn in AlSi alloys causes the formation of other intermetallic phases. To understand the effect of solidification conditions and fluid flow on the microstructure of AlSi-based alloys and the addition of Mn leading to Mn-based intermetallics, Al-5 wt pct Si 0.2/0.4/1.0 wt pct Mn alloys have been directionally solidified under defined thermal (gradient 3 K/mm, solidification velocity 0.02-0.12 mm/s) and fluid flow (rotating magnetic field 6 mT) conditions. The primary Al-phase and Mn-based intermetallic phases were studied using 3D X-ray tomography. The spatial morphology of primary phase and intermetallics were characterized with respect to different fluid flow and solidification conditions. The tomography has showed the 3D complicated structure of Mn phases developed.

Mushy Zone Morphology Calculation with Application of CALPHAD Technique

“…Specimens with manganese show some enrichment in the center (e.g., AlSi9Mn1.0), but also some enrichment outside the center (e.g., AlSi5Mn1.0). This seems to result from different morphologies between platelet shaped β-Al 5 FeSi and complicated shaped Mn-rich phases [26].…”

“…Such a possibility depends strongly on the dimension and morphology of intermetallics. According to [26], we may distinguish Mn phases with different morphologies: cube, colony of cubes, tree shaped, platelet shaped, and rib shaped phases. In addition, the formation of other phases caused by the presence of additional alloy components (e.g., Mg) might decrease the fluidity of the solidifying melt [27].…”

Thermo-Calc Prediction of Mushy Zone in AlSiFeMn Alloys

“…Specimens with iron and manganese show slightly irregular values across the sample, with some enrichment in the center (e.g., AlSi5Fe1.0Mn0.4), but also near the outside (e.g., AlSi5Fe0.2Mn0.2). The morphologies of platelet-shaped β-Al 5 FeSi and complex Mn-rich intermetallics seems to be the primary factor influencing the enrichment in the center and some outside [34]. α-Al dendrites form a skeleton structure with a liquid channel in the center.…”

“…Current results conducted for 5% Si are similar to [31,33] The possibility of Fe-or Mn-phases moving through the liquid depends strongly on the morphology and dimension of intermetallic Fe-and Mn-phases, and the differences in the shape are well visible on Figure 13. Iron intermetallics form platelets [22] with various dimensions from a few micrometers to 1 mm, while Mn-rich phases [34] may take a shape ranging from compacted cubes (100 µm) to a large complex colony of cubes reaching above 1 mm. The fluidity of the solidifying melt might be decreased by the growth of other phases, e.g., Mg 2 Si in Mg containing alloys [35].…”

Morphology and Distribution of α-Al and Mn-rich Phases in Al-Si-Mn Alloys under an Electromagnetic Stirring

“…Main alloying elements in casting alloys are Cu, Si, and Mg, whilst the main impurities are iron (Fe), manganese (Mn) and zinc (Zn) in recycled alloys. Iron is the most harmful element causing formation of long intercepting platelets leading to unacceptable mechanical properties, thus alloying elements such as Be, Mo, Cr and especially Mn have been used to replace needle shaped β-Al5FeSi phases with α-Al(Mn,Fe)Si skeleton or granular (or Chinese) morphology [1][2][3].…”