Coordination Number, Packing Factor and Slip Systems in BCC, FCC and HCP Structures

engineers.academy/
This video outlines different crystalline structures including body centred cubic (BCC), face centred cubic (FCC) and hexagonal close packed (HCP).
The tutorial explains how to determine coordination number and packing factor for each unit cell and explains how this can influence the properties of the material.
Finally, slip systems are discussed for each structure by first identifying the slip planes and slip directions of each plane. Again, this is related to the properties of given materials.
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[@yerkoc37]

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[@chicns1122]

Thank you!

[@annamalaia8589]

Thank you sir🙏

[@ianvangiesen2523]

Is there a visual explanation somewhere that clearly describes (even if tediously) the closest packed planes and slip systems/planes for the BCC lattice? It's pretty frustrating how easy it is to visualize the fcc and hcp compared to the bcc.

[@EngineersAcademyLTD]

Thanks Ian. Unfortunately I haven't been able to find anything, despite spending quite a bit of time searching. Please let us know if you find anything.

[@1hasny]

How do you determine the number of slip planes in the BCC structure? I don't see how there would be 18 planes.

[@EngineersAcademyLTD]

Hi Hasan. This is a slight simplification as it depends on the material. If we take tungsten (W) as an example, there are 6 {110} slip planes and 12 {211} slip planes. It is still quite hard to visulalise, but hopefully this image will help: images.slideplayer.com/13/3815885/slides/slide_4.jpg Note that alpha iron has an additional 24 {321} slip planes.

[@ianvangiesen2523]

@@EngineersAcademyLTD Unfortunately that image does not include a coordinate, so in comparison of the respective, albeit unmarked, {110} and {211} planes, {211} is both drawn confusingly, and I believe wrong, as the {211} plane should intersect the x-plane within in the unit cell, instead of outside. I believe a {122} plane was drawn instead of a {211} plane. Just to help people avoid confusion.

[@EngineersAcademyLTD]

@@ianvangiesen2523 thank you for you feedback. I agree it is certainly difficult to visualise, but for our programmes the important thing is how the material properties are affected by the presence of slip systems. It is probably not a sufficient explanation for someone studying material science, as an example.

[@nomipakistanli]

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