Commercial niobium alloys are poor in strength and malleability, with 70% of niobium alloys requiring cold processing prior to annealing. As a result, niobium alloy with complex structure and low density can be easily manufactured. People generally prefer niobium to other refractory metals such as molybdenum, tantalum and tungsten. In the 1960s, many high-temperature niobium alloys were developed, mainly for nuclear weapons and space applications; However, further development has been limited since the early 1970s. Today, niobium is also used in smart human devices. Transport satellites and a wide range of high temperature components, however, due to their sensitivity to oxidation and prolonged operation at high temperatures, these alloys will be more widely used in other applications.
Although these elements improve the strength and hardness, toughness, sensitivity and texture of the alloy equal or better than pure niobium, in most cases, the alloying of niobium with tantalum, titanium and vanadium is rapid and the forming process is complex. All other alloying elements greatly reduce toughness, sensitivity and texture. In general, niobium alloys are more tolerant of picking up impurities than other opposite metals (e.g., Zr, Ti), because these impurities can greatly reduce the elongation, mainly the grain edge. For example, when copper is added, the mechanical properties of these alloys become significantly worse.
In order to improve their oxidation resistance at high temperatures, niobium alloys are extensively coated with special processes, such as silicon. Most niobium alloys are prepared by electron beam, plasma and vacuum arc smelting with appropriate additions. For large ingots, it is required to produce an appropriate ingot with the right ingredients in two melting runs. Today, most common alloy additives are titanium, zinc, tungsten, tantalum and hafnium, into which they enter steadily during smelting.
Another promising niobium alloy production method is electrodeposition from molten salts, such as deposition from the KEL-KF-K2ZRF6-K2NBF7 system.
Niobium alloys can also be prepared by powder metallurgy. Several methods can be used to prepare niobium powders, including gas-atomization, calcining and quenching, mechanical fusion, high-temperature diffusion, or hydride dehydrogenation processes. However, when using these methods, oxidation, impurity introduction are difficult to avoid and expensive.
