Applications
Titanium metal and its alloys have a wide range of applications, where the corrosion resistance, the heat stability and the low density (light weight) are of benefit. The foremost use of corrosion-resistant hafnium and zirconium has been in nuclear reactors. Zirconium has a very low and hafnium has a high thermal neutron-capture cross-section. Therefore, zirconium (mostly as zircaloy) is used as cladding of fuel rods in nuclear reactors, while hafnium is used as control rod for nuclear reactors, because each hafnium atom can absorb multiple neutrons.
Smaller amounts of hafnium and zirconium are used in super alloys to improve the properties of those alloys.
Read more about this topic: Group 4 Element