The main strengthening ways of niobium are solid solution, precipitation and deformation heat treatment. In Nb alloy, the high and low temperature strength of Nb alloy can be significantly improved by containing tungsten and molybdenum, but too much will reduce the technological properties of Nb alloy. Tantalum is a medium strengthening element and can reduce the plasticity-brittle transition temperature. Another way to strengthen Nb alloy is to add titanium, zirconium, hafnium and a certain proportion of carbon to form a diffuse carbide phase for precipitation strengthening. In addition, these active elements can also improve other properties, such as titanium can significantly improve the oxidation resistance and process properties of the alloy; Hafnium and zirconium can improve the corrosion resistance of molten alkali metal. Hafnium can significantly improve the oxidation resistance and welding property of the alloy. The high strength niobium alloy generally contains a large number of solid solution elements (tungsten, molybdenum, tantalum, etc.) for solid solution strengthening, and precipitation strengthening is also used to make the alloy have high strength (see metal strengthening). The plastic processing of these alloys is difficult and the deformation parameters need to be strictly controlled. In addition to Nb-10W-1Zr-0.1C alloy containing carbide precipitation strengthening phase, the other varieties are added with medium content of solid solution strengthening elements to ensure that they have excellent comprehensive properties. As long as proper amount of titanium, zirconium and hafnium is added to the low strength alloy, it can ensure that the alloy has excellent processing properties.
Niobium can be prepared by point melting of potassium sevafluorniobate or by reducing niobium pentoxide with sodium sea fluorniobate or aluminum. Pure niobium is used in vacuum tube to remove residual gas. Addition of niobium in steel can enhance the oxidation resistance of steel at high temperature and improve the welding property of steel. Niobium is also used in the manufacture of high temperature cermets.
Niobium and niobium alloy tubes, rods and wires are widely used in the fields of chemistry, electronics, aviation and aerospace due to their high melting point, corrosion resistance and good cold working performance. Niobium and niobium alloy rods are used as structural materials for aero engines and rocket nozzles, reactor internal components and cladding materials, and to make corrosion resistant parts under nitric acid, hydrochloric acid, or sulfuric acid corrosion conditions. Adding zirconium to niobium can obviously improve the oxidation resistance and strength of the material, niobium and niobium zirconium alloy wires are widely used in the manufacture of high pressure sodium lamps and anode leads of electrolytic capacitors.
