Avik Mahata

Bricks of different sizes laid in a single wall leave cracks in it. Atoms in superalloys behave much the same way: when two different metals form a common crystal lattice and their atoms differ slightly in size, stress appears inside the material. It accumulates and eventually destroys the alloy when heated.

Tungsten is a true heavyweight among metals. It withstands monstrous heat and isn't afraid of radiation, which is why it's prized in fusion reactors. But there's a catch: at room temperature, it behaves like a piece of glass: it cracks on impact instead of bending.