Tantalum alloy is an alloy composed of tantalum and other elements. The anodic oxide film of tantalum is very stable, corrosion-resistant, and has excellent dielectric properties, which is suitable for electrolytic capacitors. Tantalum has strong resistance to chemical corrosion. It can resist the corrosion of all organic and inorganic acids except hydrogen fluoride, sulfur trioxide, hydrofluoric acid, hot concentrated sulfuric acid and alkali, so it can be used as corrosion resistant material in chemical industry and medicine. Tantalum carbide is an important additive in the manufacture of hard alloy. Tantalum is also used in some electronic tubes. In 1958, Ta-10W alloy was put into production. In the 1960s, tantalum alloy was used in the aerospace industry as a high-temperature structural material. Tantalum and tantalum alloy products include sheet, strip, foil, bar, wire, shaped parts and sintered products.
Among refractory metals, tantalum has the best plasticity at low temperature, and its plastic-brittle transition temperature is lower than -196℃. The excellent low temperature plasticity of tantalum must be considered in the development of tantalum alloys. Tantalum alloys are mostly strengthened by solid solution, or by combining solid solution and precipitation strengthening to improve their strength. In the periodic table, some tantalum adjacent elements can be completely solid dissolved in tantalum, and some have high solubility. The replacement solution elements with the most obvious strengthening effect are rhenium, tungsten, zirconium and hafnium. If the amount of added elements exceeds a certain range, the low temperature plasticity of tantalum will be damaged. It is generally accepted that the percentage of added atoms should be less than 12 ~ 14%. Gap elements such as nitrogen, carbon and oxygen have little effect on enhancing the strength of tantalum, but significantly damage its low temperature plasticity and processing plasticity. When these interstitial elements form a dispersive precipitated phase with the active elements zirconium or hafnium, the strengthening effect is obvious. The Ta-10W-2.5Hf-0.01C alloy developed from Ta-10W is a typical alloy which combines solid solution and precipitation strengthening.
The plasticity of pure tantalum is good, the deformation resistance is small, the work hardening rate is small, all kinds of profiles and special-shaped parts can be obtained by plastic processing method. Pure tantalum can be rolled into sheet, strip, foil, tubing and bar at room temperature with a processing rate of more than 90%. In order to reduce oxidation, plastic processing of pure tantalum is usually carried out at room temperature or below 500℃. Tantalum alloy due to high strength and poor plasticity of ingot casting, must first be opened above 1200℃, after the processing process is the same as pure tantalum. The extrusion ratio of the blank should be greater than 4, and the forging ratio should be greater than 2. When the billet is heated, the plastic drop of the material should be prevented from gas pollution. In order to ensure good stamping and spinning properties of the product, cross rolling is used. The processing rate before cross rolling should be maintained at about 80%. Tantalum board can be made into cup, cap, tube, cone, nozzle and other parts with different shapes by spinning and deep drawing. The diameter of rotary forging bar for drawing is generally 2.5 mm. Because tantalum is soft, it is easy to bond with the mold and scratch the surface, so the wire surface is often anodized to form an oxide film and lubricated with beeswax.
