The main strengthening ways of niobium are solution, precipitation and deformation heat treatment. In niobium alloys, the alloys containing tungsten and molybdenum can significantly improve their high and low temperature strength, but too much content will reduce the process properties of the alloys. Tantalum is a medium strengthening element and can reduce the ductility - brittleness transition temperature of alloys. Another way to strengthen niobium alloys is to add titanium, zirconium, hafnium and a certain proportion of carbon to form a dispersed carbide phase for precipitation strengthening. In addition, these active elements can also improve other properties, such as titanium can obviously improve the oxidation resistance and process properties of the alloy; Hafnium and zirconium can improve the resistance of the alloy to molten alkali metal corrosion; Hafnium can significantly improve the oxidation resistance and weldability of the alloy. High strength niobium alloys generally contain a large number of solid solution elements (tungsten, molybdenum, tantalum, etc.) for solution strengthening, and precipitation strengthening is also used to make the alloy have high strength (see strengthening of Metals). 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, other kinds of medium strength alloys are added medium content of solid solution strengthening elements to ensure excellent comprehensive properties. Low strength alloys can be guaranteed to have excellent workability by adding appropriate amounts of titanium, zirconium and hafnium.
The metal niobium can be prepared by point decomposition of potassium sevoflurniobate, or by reducing niobium pentaoxide with sodium sevoflurniobate or aluminum. Pure niobium is used to remove residual gas in electron tubes. Niobium doped in steel can improve the oxidation resistance and weldability of steel at high temperature. Niobium is also used in high temperature cermet.
Niobium and niobium alloy tubes, niobium alloy rods and niobium alloy wires are widely used in chemical, electronic, aerospace and other fields because of their high melting point, corrosion resistance and good cold working properties. Niobium and niobium alloy bars are used as structural materials for aero-engines and rocket nozzles, as internal components and cladding materials for reactors, and as corrosion resistant parts for nitric acid, hydrochloric acid, or sulfuric acid. 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 lamp and electrolytic capacitor anode leads.
