A helix functions as a grain selector. I think that only the crystal with axial alignment is fastest in general at propagating through a spiral. Animation of t

A helix functions as a grain selector. I think that only the crystal with axial alignment is fastest in general at propagating through a spiral. Animation of the effect: https://www.youtube.com/watch?v=br9iaeYYxSM https://www.youtube.com/watch?v=br9iaeYYxSM Paper on the development of single crystal casting: http://www.tms.org/superalloys/10.7449/2008/Superalloys_2008_367_374.pdf http://www.tms.org/superalloys/10.7449/2008/Superalloys_2008...