Full Record for Micrograph 712
.. in new window
View micrograph and record
.. in new window
You can also view and download the micrographs on Flickr
- Micrograph no
- Brief description
- As-cast wrought-grade aluminium alloy (Al-Mg-Fe-Si containing < 1wt.% of each solute). Addition of TiB2 particles facilitates the formation of a fine, equiaxed grain structure (grain refinement).
- alloy , aluminium , anodising , dendrite , equiaxed , iron, magnesium, metal, silicon
- Metal or alloy
- Not specified
- Standard codes
- Sample preparation
- Electrolytically etched using Barker's reagent.
- Cross-polarised light microscopy
- Length bar
- 400 μm
- Further information
- This micrograph illustrates one of the possible growth morphologies that a solidifying metal can adopt (c.f. micrograph 711). The grains in this structure exhibit no dendritic branching, i.e. the solid-liquid interfaces of the growing grains are smooth. When a solid grain is growing from the liquid phase, it will initially exhibit a smooth interface; such an interface can become unstable as the grain becomes larger due to rejection of solute into the liquid phase. Hence, smooth grain boundaries are associated with fine grain structures and low solute contents.
The Barker's etch and applied electrical field produce a thick oxide layer on the grains of aluminium (anodising). When viewed in cross-polarised light, interference in the oxide layer produces colours which depend on grain orientation; hence the grain structure is imaged.
- T Quested
- Department of Materials Science and Metallurgy, University of Cambridge
- Licence for re-use
- Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
- Related micrographs
- Micrograph 710: Wrought-grade aluminium alloy (Al-Mg-Fe-Si containing < 1wt.% of each solute); refined with TiB2 particles. Deformation of grain structure is due to cutting of sample with scissors. (400 μm)
- Micrograph 711: As-cast wrought-grade aluminium alloy (Al-Mg-Fe-Si containing < 1wt.% of each solute). No addition of grain refinement particles (e.g. TiB2). (1 mm)