If you think this is neat, you'll probably also like the "grain selector" technique they use to cast single crystal turbine blades. This is useful for the blade

If you think this is neat, you'll probably also like the "grain selector" technique they use to cast single crystal turbine blades. This is useful for the blades operating in the hottest parts of the turbine, and helps avoid creep deformation. To do this, they add a little spiral to the end of the wax turbine blade pattern before making the investment casting. The mold is then filled with molten metal, and the entire casting is moved very slowly through a temperature controlled furnace with a hot and a slightly-less-hot zone. The metal solidifies at the interface between those two zones, and as the solidified "front" passes through the spiral, one crystal orientation ends up winning out, and then the remainder of the turbine blade solidifies into a crystal with that orientation. There's not a lot of public information about this process (lots of trade secrets), but it's super cool. https://www.americanscientist.org/article/each-blade-a-single-crystal https://www.americanscientist.org/article/each-blade-a-singl... https://www.youtube.com/watch?v=zkUN9ch07dM https://www.youtube.com/watch?v=zkUN9ch07dM Apparently they use a somewhat similar dual-furnace technique to grow single crystal boules of III-V semiconductors like GaAs: https://en.wikipedia.org/wiki/Bridgman%E2%80%93Stockbarger_technique https://en.wikipedia.org/wiki/Bridgman%E2%80%93Stockbarger_t...