5. Powders

The metallurgy of Zr or Hf powders is rather limited, due to their easy flammability and risk of explosion. Three powder production methods are used.

• The reduction of various Zr compounds by calcium yields a relatively impure powder used for pyrotechnic applications, but not suitable for making parts by powder metallurgy processes.

• Chemical etching with a strong acid (HCl, H ₂ SO ₄ ) of the Zr-Mg pseudo-alloy from the Kroll reduction removes Mg and yields a completely fine, spherical powder around 10 µm in diameter. With the exception of the residual magnesium content (approx. 1%), this powder has the same purity as sponge and can be compressed and sintered. This powder is mainly used in the armaments...