Tantalum alloy with high melting point, good conductive thermal conductivity, high chemical stability, excellent high temperature strength, good processability, weldability and low plastic brittle transition temperature, dynamic mechanical properties and excellent after oxidation treatment surface density, stable, high dielectric constant of the amorphous characteristics of oxide film is widely used in electronic, chemical, aerospace, military weapons, medical and health care and other fields. Tantalum metal is mainly used in the electronic industry. Tantalum capacitors are small in size, large in capacity, high in reliability, long in life, good in voltage resistance and stable in function. It is widely used in communication, computer integrated circuit, automobile electronic control system, digital electrical appliances and other aspects. The shell of the whole tantalum capacitor is a deep drawn cup protruding part. The tantalum plate produced in China is prone to cracking, wrinkling, orange peel, ear making and other phenomena during the deep drawing and stretching of the tantalum shell. The finished product rate is low, which makes it difficult to meet the requirements of high performance and high reliability. At present, the influence of cold deformation and heat treatment on mechanical properties of tantalum plate has not been studied. In this paper, the mechanical properties of tantalum and the mechanical behavior of tantalum tensile deformation are studied by means of control based on the engineering application background of tantalum capacitor tensile stamping, so as to provide a theoretical basis for the formulation of tantalum deep drawing processing technology.
The experimental material is pure tantalum ingot smelted by secondary electron beam. The cast ingot is forged and rolled to obtain 4mm thick plate, and then through cross rolling to obtain 1mm and 1.6mm thick plate. Recrystallization annealing was carried out at 900℃ and the holding time was 15, 30 and 45min respectively. Finally, the specimen was stretched under the condition of strain rate of 20mm/min.
After recrystallization annealing temperature was selected at 900℃ and held for 15, 30 and 45 minutes respectively, the microstructure of thin plate samples with a thickness of 1 and 1.6mm was observed. The results showed that the deformation structure was basically eliminated, but the refining effect of recrystallization structure was not obvious. When the cold deformation is small, higher recrystallization annealing temperature should be used to refine the grains. The specimens with a thickness of 1 and 1.6mm were predeformed by 10% and 20% respectively, and then recrystallized by annealing at 900℃. After the treatment, the hardness and tensile strength of the two specimens increased, but the elongation significantly decreased. This is the result of the preponderance of the work hardening and recrystallization softening of the material. After 15, 30 and 45min of heat preservation, the hardness of tantalum increases gradually with the extension of heat preservation time, while the elongation decreases successively. With the extension of the heat preservation time, the yield strength of materials with different thickness gradually increased, but the tensile strength of 1mm thick plate gradually decreased, while that of 1.6mm thick plate first decreased and then increased. The morphology analysis of tensile fracture shows that after predeformation and heat treatment, the material changes from ductile fracture to brittle fracture, and the fracture mechanism is mixed fracture, which is composed of intergranular fracture, cleavage fracture and ductile fracture. The morphology analysis of fracture is consistent with the mechanical properties.
