Refractory molybdenum and its alloy features:
High melting point, low expansion coefficient, good thermal conductivity, excellent corrosion resistance and high strength, hardness, stiffness and thermal shock resistance at high temperature.
Refractory molybdenum and its alloys are widely used in national economic construction, national defense construction, and scientific research. Molybdenum and molybdenum alloys are widely used in the application of vacuum electronics industry. Due to the particularity of the electronic vacuum industry, the demand for molybdenum and molybdenum alloy materials is stringent. And the variety of all kinds of products are various and different specifications. There are special requirements for silk, bar, sheet, and foil. For example, the plasticity, toughness, ductility, high-temperature resistance, powder shape, and particle size distribution. Electric vacuum devices are required to have a high melting point, high-temperature strength, and light specific gravity. Therefore, molybdenum bar is undoubtedly the best choice.
At present, most of the molybdenum bars are produced by rotary forging in China. After forging, the molybdenum bars cannot be directly used because they have high internal stress, uneven grain structure and are easy to be a brittle fracture in later processing. The molybdenum bar is inconvenient for processing. In this paper, the effect of different annealing temperatures on the microstructure and mechanical properties of the 3. 0 mm molybdenum rod prepared by rotary forging was investigated. Finally, a set of cognitive annealing process was determined to make the properties of treated molybdenum bar better than ASTM standard.
(1) Annealing treatment has a significant effect on the microstructure of the 3.0mm molybdenum rod used in electric vacuum devices.
For the horizontal organization, between 800 ~ 950 ℃, and microstructure of molybdenum rods isometric some small particles, some like corrugated overlapping between grain. In 1 000 ~ 1 200 ℃ between, between the grain size of corrugated overlapping almost disappear. For vertical organization between 800 ~ 950 ℃, and microstructure of molybdenum rods is stable. The tissue is fibrous. The aspect ratio of grain decreased. Between 1 000 ~ 1 200 ℃, molybdenum rods of fibrous tissue has not entirely disappeared, and partial recrystallization grains. If complete recrystallization is to be obtained, the annealing temperature should be further increased.
(2) Annealing treatment has a significant impact on the mechanical properties of the 3.0 mm molybdenum rod used in the electric vacuum. devices.
When the annealing process is 950 ℃ heat , molybdenum rods of room temperature mechanical properties to achieve the optimal. The maximum tensile strength is 777 MPa.The maximum elongation was 49.5 %. Mechanical properties are better than ASTM standard.