Molten aluminum (~850 C) is poured in a graphite crucible, where it undergoes slow crystallization process. Since in this case process is relatively slow, the formation of crystal structure is observable on the surface.
Here by crystallization means solidification. That happnes when abmiet temperature is lower than melting temperature ( in case of aluminum 660 C). Grain size of solidified metal depends on how quickly cooling process happens. Slow crystallization means coarser grain sturcture.
@@MHDTechnologyLaboratory That doesn't explain why I had a "normal" aluminum pour on my first attempt, then on the following day's melt and pour, I had an even more dramatic "muffeting" type of crystallization episode. The alum rose and sputtered above the mold, like it was possessed! I also had a huge amount of "dross" or slag before that pour. I've been hesitant to attempt my 3rd melt & pour, until I find a reasonable explination for this incident. I have 300+ lbs of aluminum waiting to be melted down & poured. Thanks for the response!
