The main ways of strengthening niobium are solution, precipitation and deformation heat treatment. In niobium alloy, tungsten and molybdenum can significantly improve the high and low temperature strength, but too much content will reduce the technical performance of the alloy. Tantalum is a medium strengthening element and can reduce the plastic-brittle transition temperature of the alloy. Another way to strengthen niobium alloy 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 significantly improve the oxidation resistance and process performance of the alloy; Hafnium and zirconium can improve the corrosion resistance of molten alkali metal; Hafnium can significantly improve the oxidation resistance and welding performance of the alloy. High strength niobium alloys generally contain a large number of solid solution elements (tungsten, molybdenum, tantalum, etc.) for solid solution strengthening, and precipitation strengthening is also used to make the alloys have high strength (see strengthening of metals). The plastic machining of these alloys is difficult and the deformation parameters need to be controlled strictly. In addition to Nb-10W-1Zr-0.1C alloy which contains carbide precipitation strengthening phase, other kinds of medium content of solid solution strengthening elements are added to ensure excellent comprehensive properties. As long as appropriate amount of titanium, zirconium and hafnium is added to low strength alloy, the alloy can be guaranteed to have excellent machining properties.
Niobium metal can be prepared by point hydrolysis of molten potassium heptafluoroniobate, or sodium potassium heptafluoroniobate or aluminum reduction of niobium pentoxide. Pure niobium is used in vacuum tube to remove residual gas. The addition of niobium in steel can improve the oxidation resistance and welding performance of steel at high temperature. Niobium is also used in the manufacture of high temperature cermet.
Niobium and niobium alloy tubes, niobium alloy rods and niobium alloy wires are widely used in the fields of chemistry, electronics, aviation and aerospace because of their high melting point, corrosion resistance and good cold working performance. Niobium and niobium alloy bars are used as structural materials for aircraft engines and rocket nozzles, reactor internal components and cladding materials, and to make corrosion-resistant parts under conditions of nitric, hydrochloric, or sulfuric acid corrosion. 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 anode leads of electrolytic capacitors.
