system
Given the following post, respond as if you're commenting on Reddit:
human
Why is tungsten at room temperature so brittle? Since super cooled metals are more brittle, is this the same phenomenon but just at a much lower temperature because tungstens melting point is so high? Or is it something entirely different?
gpt
Basic answer is that tungsten is Body Centered Cubic (BCC) and therefore will go through a ductile to brittle transformation at certain temperatures.  DBTT (Ductile to Brittle Transition Temperature) of tungsten is quite high, around 400K.  Room temperature, or 273K, is way below this transition temperature, so the tungsten will be brittle.

The basic mechanics here is that below this temperature there isn't enough vibrational energy in the lattice to allow for slip.  So the atoms are almost locked in place and are unable to slide past each other, therefore they will separate and the material will fracture.