Zirconium alloys and its applications

Zirconium alloys are solid solutions of zirconium or other metals and are a common subgroup bearing the trade mark Zircaloy. Zirconium has an extremely low thermal neutron absorption cross section,high hardness, ductility and corrosion resistance.One of the main uses of zirconium alloys is in nuclear technology as cladding for fuel rods in nuclear reactors, especially water reactors.The typical composition of nuclear-grade zirconium alloys is more than 95% by weightzirconium and less than 2% tin, niobium, iron, chromium, nickel and other metals, which are added to improve mechanical properties and corrosion resistance.The water cooling of reactor zirconium alloys increases the requirements for its resistance to oxidation-related nodular corrosion.In addition, the oxidation reaction of zirconium with water releases hydrogen, which partially diffuses into the alloy and forms zirconium hydride.Hydrides are less dense and mechanically weaker than alloys; their formation leads to blistering and cracking of the cladding a phenomenon known as hydrogen embrittlement.

Development

Rickover selected zirconium as the structural material for high-flux zone reactor components and as cladding for fuel pellet tube bundles for prototype submarine reactors.The choice was due to the combination of strength, low neutron cross-section and corrosion resistance.Zircaloy-2 was developed inadvertently by melting Zircaloy-1 in a crucible previously used for stainless steel.Newer alloys that do not contain nickel include Zircaloy-4, ZIRLO, and M5 (with 1% niobium).

Applications

Zirconium alloys are corrosion-resistant and biocompatible, so they can be used in body implants.In one specific application, Zr-2.5Nb alloys were formed into knee or hip implants and then oxidized to create a hard ceramic surface for supporting polyethylene components.This zirconia alloy material provides the beneficial surface properties of ceramics (reduced friction and increased wear resistance) while retaining the beneficial bulk properties of the underlying metal (manufacturability, fracture toughness and ductility) for these medical implants. Provides a good solution application.After the end of the Cold War, Russian demand for zirconium decreased due to nuclear demilitarization, leading to exotic production of household zirconium items such as the vodka tumbler pictured here.