3. Hafnium

Hafnium, which lies just below zirconium in Mendeleiev's periodic table, has many analogies with zirconium in terms of heat treatment, induced by similarities in crystallographic structure, texture, β – α phase transformation, its reactivity with oxygen, the formation of intermetallic phases with iron and so on. However a number of specific features need to be taken into consideration:

• hafnium alloys are generally less loaded with additive elements than zirconium alloys;

• the β – α phase transformation takes place at around 1,750°C instead of 863°C for zirconium, which makes it very difficult industrially to design ranges with β phase transition and therefore with quenching. All deformation is therefore carried out in the α phase: typically at around 1,000°C for ingot roughing, and cold for thin products;...