Molybdenum wire has good properties such as high strength, high wear resistance, high melting point, low coefficient of expansion, good thermal conductivity and thermal conductivity, but its shortcomings such as room temperature brittleness and high plastic-brittle transition temperature greatly affect its processing and application. The lanthanum-doped molybdenum wire doped with a small amount of lanthanum oxide not only improved the structure and properties of molybdenum wire, but also strengthened the strength and toughness.
Lanthanum-doped molybdenum wire preparation processes are as follows:
- MoO2 as raw material doped with La (NO3) 3 aqueous solution, and the doping powder should be dried, homogenization and hydrogen reduction after well mixing to obtian doped molybdenum powder.
- Doped molybdenum powder through cold isostatic pressing and intermediate frequency sintering was made of 48mm diameter molybdenum rod.
- Molybdenum rod processed heating, cogging, drawing and other processing system was made of Ø0.75mm lanthanum-doped molybdenum wire.
The recrystallization temperature of doped lanthanum molybdenum wire is higher than pure molybdenum wire, which has better high temperature performance. Besides, the aspect ratio of grain structure becomes larger after recrystallization, which is beneficial to its performance improvement. In addition, the tensile strength of lanthanum-doped molybdenum wire annealed at different temperatures was enhanced by the second phase dispersion strengthening of La2O3 particles, which was about 110 ~ 200MPa higher than that of pure molybdenum, and annealing temperature was increased by 250 MPa at processing state. The doping amount of La2O3 is small (about 300 ± 50mg / kg), which is conductive to the subsequent processing of molybdenum wire. What’s more, the wire breakage rate is lower than pure molybdenum wire’s, but also it is superior to molybdenum wire with high doping content.
Form the above information shows that the comprehensive performance of molybdenum wire with micro-doped La2O3 is better than pure molybdenum wire. Compared with pure molybdenum wire, molybdenum doped molybdenum wire significantly improved the strength and toughness, increased its room temperature strength and recrystallization temperature, improved the room temperature brittleness after recrystallization, so its comprehensive performance is better than pure molybdenum wire , also better than high-doped lanthanum molybdenum wire. Further lanthanum doping amount at 290mg / kg is the best.